Health & Management / Ruminants Pain Management / Techniques and protocols OVERVIEW:
Pain Prevention for Lamb Castration and Tail Docking:
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Introduction and General Information

Castration and tail docking of lambs are common management procedure which may be carried out by a variety of methods. They are normally carried out at the same time (in male lambs) and are therefore considered together.

Methods of castration

  • Surgical castration: Incisions are made in either side of the scrotum, or the distal third of the scrotum is cut off, revealing the testes. The testes are removed by drawing them out without cutting the spinal cords or after scraping and cutting, clamping or cauterising the cords. (J10.48.w4, J10.39.w3)
    • Haemorrhage from the spermatic and epididymal arteries is reduced/eliminated by twisting and tearing of the spermatic cords (most commonly used in lambs) or by emasculators, cautery or ligatures. (J15.14.w3)
    • Since the testes are removed these can no longer provide either a source of pain or a source of infection, although the incision(s) in the scrotum can still do so. (J15.14.w3)
  • Clamp (Burdizzo) castration: A specially designed instrument, such as the Burdizzo, is applied to both spermatic cords in such a manner as to crush the spermatic cords (thereby damaging the blood supply to the testes) without breaking the skin. (D153.II.w2)
    • The spermatic cord including blood vessels is crushed by applying a clamp, without the medial scrotal tissues being crushed. The clamp may be applied once or it may be applied twice. (J10.48.w4)
    • High pressure is applied to the spermatic cord over about a 3 to 5 mm band; the skin remains intact and usually recovers. (J15.14.w3)
    • The clamp is often applied twice, the second application being distal to the first. (J15.14.w3)
    • Careful application allows collateral circulation to the scrotum to remain. (J15.14.w3)
    • Effective application of the clamp requires a certain amount of skill and also awareness of the underlying anatomy. (J15.14.w3)
    • This method is not generally used with small lambs as it is difficult to apply the clamp sufficiently precisely to the spermatic cords. (J15.14.w3)
    • Potential problems associated with this method include incomplete castration and injuries/infection associated with poorly maintained implements. Problems are likely to be worse where bloodless castrators are applied for shorter than recommended times, have not been stored properly and when the wrong size is used. There appears to be considerable variation not only between makes but also between individual instruments in the pressure produced by application of the bloodless castrators. Application times used by farmers are commonly lower than the time recommended. (J35.152.w2)
    • There is a risk that this procedure may not be effective and that a testis may remain intact. (J10.45.w3)
    • If applied twice then the second application must be distal to the first or further pain is caused. (J3.138.w3)
  • Ring castration: a constrictive rubber ring is applied to the neck of the scrotum using a special instrument (an elastrator), with both testes distal to the ring. Blood flow through the testes and ring is obstructed and these structures atrophy and drop off after about four to six weeks. (J10.48.w4, J15.14.w3, D153.II.w2)
    • This is an ischaemic form of castration which occludes both the arterial supply and venous drainage of the testes by application of pressure around the scrotal neck. (J15.14.w3)
    • This method is quick and easy to use. (J15.14.w3)
    • As well as rings which are "normal tension", "tight rings" of higher tension have also been used. (J10.48.w4)
    • In the UK this can only be carried out without anaesthesia in lambs of no more than one week old. (J15.14.w3)
      • On hill farms in the UK castration at less than one week of age may not be a practical option (J35.152.w2)
  • Short scrotum: A rubber ring is placed around the scrotum distal to the testes so that the testes are held against the abdominal wall. The distal scrotal skin atrophies and drops off after 4-6 weeks. (J10.39.w2, J10.48.w4)
  • Ring plus clamp: A ring is placed around the neck of the scrotum, proximal to the testes, and a clamp is applied either immediately before or after application of a ring. The clamp may be applied to each spermatic cord separately, not involving medial scrotal tissues, or may be applied across the whole scrotum. The duration for which the clamp is applied varies; one, five six and ten seconds have been reported. (J10.48.w4)
  • Chemical castration: Corrosive agents such as alpha-hydroxypropionic acid, lactic acid or formaldehyde in ethanol are injected into the testes, resulting in necrosis or sufficient testicular tissue impairment that the lambs are infertile. (J10.48.w4, J24.62.w1)

Methods of tail docking (tailing)

  • Surgical tail docking: the tail is cut off using a sharp knife; (J10.48.w4) or shears. (J15.14.w3) 
    • A twisting action, thermal cautery (sometimes incorporated in the shears) or application of a Burdizzo clamp before the tail is cut off may be used to reduce haemorrhage. (J15.14.w3)
  • Heated docking iron: the tail is severed by cautery using a specially designed heated chiselled metal device. Alternatively, less commonly, the tail is cut off with a sharp knife then the stump immediately cauterised using a heated iron. (J10.48.w4)
  • Ring tail docking: A rubber ring is applied to the tail, preventing arterial blood flow to, and venous drainage from, tissues distal to the ring. These tissues atrophy and drop off after four to six weeks. (J10.48.w4, J15.14.w3)
    • The ring must be applied in such a position that at least the anus is covered by the remaining portion of tail in male lambs and the vulva in female lambs. (J15.14.w3)
  • Ring plus clamp tail docking: A ring is placed on the tail and a clamp is then applied across the tail immediately distal to the ring. (J10.48.w4)
  • Clamp tail docking: This is not commonly used in the UK. (J15.14.w3)

N.B. In the UK, under the Protection of Animals Acts 1911 to 1988 (in Scotland, the Protection of Animals (Scotland) Act 1912 to 1988) and the Protection of Animals (Anaesthetics) Act 1954 (as amended), castration of male sheep over three months of age and male goats over two months of age must be carried out under local anaesthesia or general anaesthesia. Castration by use of a rubber ring without anaesthetic is allowed only within the first week of life. (D158, LCofC5, LCofC7)

In a survey of farmers in England and Wales in 1988-1989, 92.1% of farmers stated their method of tail docking: 86.4% used rubber rings for tail docking, 3.1% used a knife 2% used other methods (clipper, a hot iron, Burdizzo clamp or "twisting off"). (J3.131.w3)

Notes on impulse transmission following castration or tail docking by different methods:

  • When methods causing immediate, severe tissue damage are used (surgery, clamp or docking iron), there is an immediate barrage of nerve impulses in pain pathways at the time the injury is inflicted and this continues for a period after the event. This is indicated physiologically by maximal rates of rise in plasma cortisol concentrations. Following this there is usually a period of "inflammatory pain". (J10.48.w4)
  • When methods such as ring or corrosive chemical are used, there is an initial nerve impulse barrage which is followed by further tissue damage and presumably nerve impulse traffic. Submaximal rates of rise in plasma cortisol concentrations indicate that this may take 30 minutes or more to reach maximal effects. (J10.48.w4)
  • With methods such as surgery, in which transmission of impulses from the damages area are not obstructed, it would be expected that inflammatory pain would increase over a period of hours and decline as the pain-producing features of inflammation resolve. (J10.48.w4)
  • With methods such as rubber rings, in which pain impulse transmission from the affected area is progressively impeded, transmission of inflammatory nerve impulses will end earlier; with rubber rings transmission of pain impulses is impeded within about 1.5 hour of their application. (J10.48.w4)
  • With rubber rings there is an initial nociceptive barrage due to manipulation of the scrotum, testes and tail, and by application of the rings. There then appears to be nociceptive activity from the ischaemic tissues, first increasing, then decreasing over a period of one to two hours. It appears that this nociceptive activity reaches the CNS via intact nerves passing through the rings and increases as the testicular receptors are sensitized and stimulated by substances released into their microenvironment. (J15.14.w3)
    • These nociceptors can function for more than three hours after the blood supply to them has been occluded. (J15.14.w3)
  • With the Burdizzo clamp method, acute pain appears to be less intense and of shorter duration than that occurring with the rubber rings. The intense barrage which it is presumed occurs from afferent nerves in the spermatic cord and from nociceptors in scrotal tissue crushed by the clamp is thought to last only a short time: the clamp should exert sufficient pressure that the afferent nerves and nociceptors are irreversibly damaged. However, some lambs continue to show signs suggesting considerable pain; it appears likely that in these individuals conduction continues in some afferent nerves. Activity may then occur in intact nociceptors due to inflammatory processes. (J15.14.w3)
  • With surgical castration and tail docking, since the testes and distal tail are removed they cannot continue to act as a source of pain following the initial surgery. Acute pain occurring with this method is probably due to stimulation of nociceptors and afferent nerves when making the incisions and when taking actions to prevent haemorrhage, but is limited to the time taken to remove the testes and tail. Twisting and pulling the spermatic cord appears to produce a particularly intense barrage of impulses. Afterwards there is an increase in activity of remaining intact nociceptors due to inflammation which occurs first as a result of the trauma and later due to infection. (J15.14.w3)
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Reasons for the procedure

Castration:
  • To avoid indiscriminate breeding and to maintain genetic control of breeding stock. (J15.14.w3, J21.66.w1, D153)
  • To avoid behavioural problems and the risk of injuries which may occur due to sexual related behaviour and during fighting to establish a dominance hierarchy. (J15.14.w3, J21.66.w1, J35.152.w2, D153)
  • A belief (not necessarily valid for some production systems) that castration improves carcass conformation and quality, and that it is necessary to avoid downgrading of the carcass due to excessive ram characteristics. (J21.66.w1)
    • To avoid downgrading of carcasses for excessive ram characteristics. (D153, J15.14.w3)
    • To avoid potential downgrading of carcasses of uncastrated animals.(J15.14.w3)
  • To produce untainted meat and therefore qualify for a market premium. (J35.152.w2)
  • To avoid unwanted pregnancies. (J35.152.w2)
    • To prevent mating of young females before they are in an adequate physical state for pregnancy and parturition. (J15.14.w3)
  • To increase growth rates: some farmers perceive that castrated lambs fatten more quickly. (J35.152.w2)
  • To aid in fattening of lambs from breed which mature and grow more slowly. (D153)
  • To reduce transmission of venereal diseases; (J15.14.w3)

Tail docking:

  • To decrease faecal soiling in the perineal area and thereby reduce the risk of myiasis (fly strike). (J4.221.w4, J21.52.w1, D153)
    • In a survey regarding blowfly strike in England and Wales, 75.2% of farmers reported tail docking as one method of control of blowfly strike. Other methods used included dipping, dagging and crutching (partial shearing of the perineal area), spraying with insecticide and using cyromazine. (J3.131.w3)
    • A study comparing docked and undocked lambs on seven farms found that faecal soiling was slightly more common in undocked than in docked lambs and that fly strike was significantly (P<0.001) more common in undocked than in docked lambs. (J3.134.w7)
      • There was no apparent effect on growth or mortality, although the highest cumulative survival was in undocked ewes, i.e. individuals which had been neither docked nor castrated. (J3.134.w7)
      • It was noted that the results did not prove that the incidence of fly strike on a flock level was higher if lambs were undocked; it might show only that, if flies are looking for a laying site, undocked lambs will be chosen preferentially. (J3.134.w7)
      • It was noted that both the diarrhoea that leads to faecal soiling, and blowfly strike, are preventable by other means. (J3.134.w7)
  • To improve the appearance of lambs. (J21.52.w1)
    • Lambs may be docked in preparation for showing. (J4.221.w4)
  • It has been suggested that docking increases the breeding efficiency of ewes. (J21.52.w1)
  • To make management easier at mating and lambing. (D153)
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Arguments against use of the procedure

Castration:
  • Lambs are able to reach an acceptable carcass size of better quality before they reach puberty and become sexually active;
  • Uncastrated lambs grow faster and more efficiently and produce a leaner carcass;
  • There is no check to growth as a result of acute and chronic pain, stress or infection associated with castration;
  • Eliminating the procedure eliminates welfare problems of the procedure.

(J15.14.w3)

  • At least on lowland farms, it can be expected that lambs will be finished before they reach puberty at about five months old, therefore castration of these lambs to avoid unwanted pregnancies and behaviours is not necessary. (J35.152.w2)
  • Castration in very young lambs (within 24 hours of birth) causes pain and may reduce intake of colostrum and increase incidence of "watery mouth". (J35.141.w2)
  • The presumption that carcass quality and conformation will be improved by castration, and that entire animals will be downgraded due to excessive ram characteristics may not be valid for some production systems. (J21.66.w1)
  • A number of studies on castration have all shown that castrated lambs show a range of abnormal behaviours, and increases in plasma cortisol levels, which are interpreted as indicating pain and/or distress following castration. (J21.66.w1)

Tail docking:

  • Problems of faecal soiling and fly strike associated with docked tails do not occur in all flocks. (J15.14.w3)
  • Tail docking may not be required in some breeds in which the tail is naturally quite short, or in management systems in which scouring and blowfly strike are not seen. (J35.153.w2, V.w5)
  • Clipping wool from the tail may be used as an alternative to tail docking. (V.w6)

Risks associated with castration and tail docking:

  • Castration and tail docking very soon after birth may reduce intake of colostrum and therefore reduce passive immunity, since the behaviour of the lamb may be dominated by pain and this may interfere with sucking for several hours. (J15.14.w3)
  • Following surgical castration and tail docking there is a risk of haemorrhage, which may be considerable in the case of bleeding from the spermatic arteries but may not be visible since it may occur inside the abdominal cavity. (J15.14.w3)
  • During castration there is a risk of tissue (intestine, mesentry or omentum) herniating through the inguinal canal and becoming trapped by a ring, crushed by a Burdizzo clamp on externalized by surgery. Tissue is more likely to herniate when an animal is struggling or being vigorously restrained and therefore the abdominal pressure is increased. Careful examination prior to carrying out whichever method of castration is used should be used to detect any herniated tissue. (J15.14.w3)
  • Local infection may occur. The extent of this depends on the ability of the lamb to resist pathogens (its general health and immune system function) and on the availability of pathogenic organisms (reduced in clean, dry conditions). Surgical castration and tail docking provides an obvious immediate access route for pathogens, and any blood or other fluid accumulating in the scrotum provides a focus for pathogen growth. Pathogens may track up the spermatic cord to the peritoneal cavity and scirrous cord may occur if the cut end of the spermatic cord becomes chronically infected. With Burdizzo castration pathogenic microorganisms should not be able to enter as the skin is intact, however access may occur if the skin is broken at the time of application of the clamp or if ischaemic necrosis causes skin breakdown later. Absence of pathogens does not prevent sterile inflammatory processes. With a rubber ring pathogens do not usually gain access at the time of application but as the ischaemic scrotal skin breaks down pathogenic microorganisms can gain access though the ring and a mild local infection with limited inflammation, or a massive local infection and inflammatory reaction, or peritonitis, or even systemic infection may occur. (J15.14.w3)
    •  "Inflammation is usually accompanied by hyperalgesia and by continuing pain." (J15.14.w3)
    • It must be considered that intense chronic pain might occur in some lambs after castration and tail docking. (J15.14.w3)
  • A number of somatic and visceral nerves are damaged by castration and tail docking and it is possible that this may lead to development of neuropathic pain, as occurs in human amputees (phantom limb pain ). (J15.14.w3)
  • Tail docking of six weeks old by rubber ring may result in development of chronic inflammatory lesions with associated pain; this has also been noted in calves docked with rubber rings. (J35.155.w1)
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Signs/Evidence of pain associated with the procedure

It has been recognised for many years that castration and tail docking of lambs causes pain and distress. Behavioural and physiological measurements have been used to quantify the amount of pain associated with different methods and at different ages. All methods of quantifying pain have their limitations. For example there is a maximum cortisol concentration rise in response to stimulation and greater stimulation cannot cause a higher cortisol peak. In behavioural measurements there may be problems deciding which of two abnormal behaviours, such as abnormal activities or alternatively standing abnormally still, indicated worse pain.

  • "All of the methods of castration and tail docking of lambs, whether surgical or by ring or by Burdizzo clamp, carried out on unanaesthetised lambs, cause acute pain." (J15.14.w3)
  • "Available evidence suggests that all methods of castration and tailing cause pain and distress which may be detected by alterations in behaviour such as posture and activity, and by alterations in cortisol concentrations in the blood." (D153)
  • Behavioural changes due to the acute pain produced by surgical castration and tail docking are different from those seen following application of rubber rings: activity is reduced and postures are adopted which appear to be designed to reduce/avoid mechanical stimulation of inflamed and hyperalgesic tissues. (J15.14.w3)

Recent work has shown that not only is acute pain experienced in the first hours after castration, but that behavioural signs of pain are present in the three days following castration with rubber rings in lambs of one week or four to six weeks of age. (J147.11.w1)

Noxious stimuli from the scrotum may be more important than noxious stimuli from the testes in development of the acute cortisol response to castration by rubber ring or Burdizzo clamp, as indicated by a reduction in cortisol responses following full-width application of a clamp in combination with rubber rings, but not when ring application is combined with the clamp applied to the two spermatic cords individually, leaving intact scrotal tissue medially, and also as indicated by the marginal reduction in cortisol response to short scrotum versus ring castration, and the marginal reduction when local anaesthetic is injected into the spermatic cords prior to ring application, compared with the significant reduction when local anaesthetic has been injected into the scrotal neck or both testes (if this is due to leakage of local anaesthetic into the vaginal cavity). (J10.45.w3)

Scientific studies on pain associated with lamb castration and tail docking:

There are qualitative differences in the responses of individual lambs to a particular method of castration, although the qualitative responses are generally similar for a given method of castration and tailing. (J15.14.w3)

  • Recording of behaviour, using a dynamic and interactive visual analogue scale (DIVAS), and of mechanical nociceptive thresholds in lambs following castration of lambs (four to six days old) by surgery, rubber ring, or combined surgery and ring, found that behavioural (DIVAS) results indicated that surgical castration was the most painful method, then rubber ring castration, while the combined Burdizzo clamp application (across the whole scrotum) with the rubber ring reduced pain-related behaviours compared to the ring alone. Measuring the mechanical nociceptive threshold indicated that surgery produced a prolonged period of hypoalgesia (increased nociceptive threshold), suggesting response of the endogenous antinociceptive system, the rubber ring produced a period of hypoalgesia followed by hyperalgesia (increased then decreased nociceptive threshold) and the combined rubber ring plus Burdizzo produced a similar response to rubber rings but with a more pronounced hypoalgesic phase, suggesting a greater response of the endogenous nociceptive system. It was suggested that this indicates a greater initial stimulus of pain/distress when the combined method is applied than if rubber rings are applied alone and "questions the validity on welfare grounds of using a greater initial stimulus to reduce subsequent short term pain." [1997](J290.24.w1)
  • A study comparing lambs castrated and tail docked at five, 21 or 42 days old, by rubber ring application, surgical castration (including cautery of the tail stump) or ring in combination with application of a Burdizzo clamp, found behaviour indicating considerable pain in all groups of lambs in the first three hours after castration and tail docking. Lambs castrated and tail docked with rubber rings showed the most changes of behaviour, with significantly higher restlessness and abnormal lying and standing postures than those seen in other groups. Lambs in which a Burdizzo clamp was applied across the scrotum and tail for six seconds each after the relevant rings had been applied showed significantly reduced levels of abnormal behaviour compared to those in which the rings alone were applied. Surgical castration, which included for the tail application of a Burdizzo clamp prior to cutting and cautery immediately afterwards, followed by release of the clamp, appeared to cause less behavioural changes than ring application but more than ring plus Burdizzo. It was noted that more "statue standing" was seen in the labs following the surgical procedure and it was suggested that this behaviour minimises stimulation of sensitized tissues and may reduce pain suffered. There appeared to be few differences in the responses associated with the age of the lambs, although the surgical method appeared to be more painful in the five-day-old lambs than in the older groups. [1993](J21.55.w1)
  • A study comparing lambs castrated and tail docked at five, 21 or 42 days old, by rubber ring application, surgical castration (including cautery of the tail stump) or ring in combination with application of a Burdizzo clamp, found that compared to rubber ring alone the plasma cortisol concentration peak occurred earlier and was 28 nmol/lL lower; values returned to pre-treatment levels within 84 minutes compared with 96 to 138 minutes for lambs in which only the rubber rings were applied. Within the group receiving the Burdizzo-plus-ring treatment, some individuals showed a high cortisol response, similar to that seen in those receiving the rubber rings alone, while other had a lower cortisol response, similar to that seen in control handled lambs; this may be due to variation in the efficacy of application of the Burdizzo clamp. Surgical castration produced a cortisol peak earlier than that seen with application of rubber rings and levels had not returned to pre-treatment values within 180 minutes of the procedure. The faster rise to peak cortisol levels seen with the surgical procedure and the application of the Burdizzo clamp were considered to be due to immediate substantial tissue injury with these two methods while the rubber rings produce, via developing ischaemia, a slower build up of tissue damage and nociceptor activity. Lambs castrated and docked with rubber rings at 42 days old were noted to show a significant increase in abnormal behaviours and higher plasma cortisol responses between 138 and 180 minutes, while five-day-old lambs receiving the combined rubber ring and Burdizzo clamp procedure also showed a significant increase in abnormal behaviours and higher plasma cortisol responses between 138 and 180 minutes. Five-day-old lambs showed a significantly higher and earlier cortisol peak than older (21- or 42-day-old) lambs, which may be due the output of the adrenals being greater per litre of blood plasma in these smaller animals. [1993](J21.55.w2)
  • A study of behavioural signs and cortisol responses following castration and/or tail docking found that lambs of up to seven days old showed "mild distress" following tail docking and "marked distress" following castration and docking. Behavioural indicators of distress [pain] in lambs were considered to include restlessness - frequent standing up and lying down, rolling, kicking and stamping - lateral recumbency, immobility with neck extension, and hyperventilation. [1989](J21.46.w2)
    • Following tail docking with rubber rings of lambs of up to seven days old, in the first 15 to 30 minutes lambs stood up and lay down frequently and lay in an abnormal lateral position for about one third of lying observations; they also kicked, stamped, tail wagged and occasionally bleated; after about 30 minutes these behaviours became less prevalent and by 60 minutes most were lying ventrally, asleep. Plasma cortisol concentrations were slightly higher than those seen in control handled lambs and peaked at 30 minutes. (J21.46.w2)
    • When lambs of up to seven days old were both castrated and tail docked with rubber rings, in the first 15 minutes they stood and lay down again frequently, lay in lateral recumbency, commonly kicked, rolled briefly onto their backs and occasionally bleated. While lying laterally the neck was often extended and the dorsal lip curled up. Activities then declined so by thirty minutes most were lying (40% laterally, 45% ventrally), moving very little, neck extended, eyes closed, and hyperventilating (frequent deep breaths), until about 60 minutes after the procedure; after this time these behavioural signs diminished and most were lying ventrally, asleep, by 90 minutes. Plasma cortisol concentrations rose markedly, peaking at more than 40 ng/mL at 30 minutes but declining to control values (approximately 10 ng/mL) by 90 minutes.(J21.46.w2)
  • Following castration with rubber rings at one day old (first day after birth), during the first fifteen minutes lambs stood up and lay down frequently, and commonly lay in lateral recumbency with three or all four legs extended; kicking was also common, while several lambs rolled briefly onto their backs. The necks of the lambs were usually extended whether the lamb was lying laterally or ventrally, and the upper lip was often curled. Occasionally lambs bleated. Activity then decreased progressively so that by 30 minutes after ring application most were lying down, 75% laterally and 22% ventrally, with the neck extended, eyes closed and respiration deep and frequent (hyperventilating). At about 60 minutes these behaviours rapidly disappeared and may 90 minutes most animals were lying ventrally and asleep. Castrated lambs showed significantly greater integrated cortisol responses than did control handled lambs (P<0.01); the integrated cortisol responses of castrated lambs was not significantly different from the response seen to ACTH stimulation (P<0.08). [1991](J21.51.w1)
  • Goat kids castrated with rubber rings on the day after birth showed mainly standing in the first 30 minutes, with few postural changes or bleating and lateral recumbency seen only 3 to 9% of the time. After this, to 60 minutes, they mainly lay, with 33% of kids in lateral recumbency and 33% in ventral recumbency, with the neck extended, but with less obvious hyperventilation than was seen in lambs; 34% stood still during this time. By 90 minutes most were lying ventrally, asleep. The integrated cortisol response of castrated goat kids was significantly higher (P<0.01) than that of control handled kids but significantly lower (P<0.001) than that of ACTH stimulated kids. (J21.51.w1)
  • A study of lambs of about 65 days old, castrated and tail docked using rubber rings, found that while plasma ACTH and cortisol levels had returned to control levels by 2.5 to 3.0 hours after the procedure was carried out, blood pressure (systolic, diastolic, mean arterial) and heart rate were still elevated at four hours after application of the rings. It was suggested that heart rate and blood pressure measurements may be more sensitive indices of low grade pain than are plasma ACTH and cortisol concentrations, although an alternative explanation was that by four hours there is still a small shift in sympathetic tone in the absence of low-grade pain. It was noted that the time at which ACTH and cortisol concentrations peaked varied widely between lambs, from 20 to 100 minutes after application of the rubber rings, suggesting wide variation in the time to maximum pain-induced distress. (J10.50.w1)
  • A study compared the effects of different types of bloodless castrators on the behavioural and cortisol responses of four- to six-day-old lambs to castration with rubber rings plus Burdizzo (bloodless castrator clamp). There were no significant differences in the cortisol or behavioural responses depending on the type of bloodless castrator used (225mm 'baby' Burdizzo, Ritchey (Little) Nipper or a hydraulically powered instrument), but the hydraulically powered instrument produced the lowest cortisol response (not statistically significant) and it was considered by the operator to cause the least pain on application. Application of the bloodless castrator proximal rather than distal to the ring had a slightly greater effect in pain reduction but it was noted that care must be taken that application is distal to the teats, in order to ensure that the urethra is not crushed. (J35.162.w1)
  • A study compared the effects of different tail docking methods on the behavioural and cortisol responses of four- to six-day-old lambs to castration with rubber rings plus Burdizzo (bloodless castrator clamp). Use of a hot docking iron resulted in the least evidence of acute pain, while use of the Burdizzo in combination with the rubber ring resulted in less evidence of acute pain than use of the rubber ring alone. (J35.162.w1)
    • Lambs docked with the hot iron had a significant increase in plasma cortisol levels compared with control handles lambs and did show significantly more time in some abnormal postures and also trembling, but trembling occurred in only the first six minutes while active behaviours and time spent in normal lying postures were not significantly altered. Use of the combined ring plus Burdizzo tail docking method resulted in a significantly higher (p<0.05) restlessness score than following use of the hot docking iron, but lower increases than those seen when rubber ring tail docking was used. Use of the ring alone for docking produced a significantly higher score for limb and tail activity as well as significantly higher peak cortisol and area under the cortisol curve and the area under the cortisol curve was not significantly different from that seen with rubber rings alone used for both castration and docking. With use of a rubber ring alone for both castration and tail docking peak cortisol response, incidence of active behaviours, and time spent in abnormal postures were all significantly higher than with any of the tail docking methods together with the combined (rubber ring plus Burdizzo) castration. (J35.162.w1)
  • A study compared acute cortisol responses of lambs of about 50 days old when castrated and tail docked using rubber rings alone, ring alone for tail docking and ring plus clamp, applied distal to the ring to each spermatic cord but not to the central scrotal tissue, for castation, and ring plus clamp for both scrotum and tail, again with the median portion of the scrotum not crushed by the clamp. The study did not show any difference in cortisol secretion depending on whether or not the clamp was used. [1997](J24.75.w2)
    • All three groups showed significant cortisol responses (P<0.001) following the procedures, peaking at 30 (ring-and-clamp castration, ring tail docking) or 45 minutes (other groups). There were no significant differences in plasma cortisol responses between the groups of lambs other than that at 30 minutes the mean cortisol concentration of lambs in the group with ring-and-clamp castration, ring tail docking was significantly higher than that for the ring castration, ring tail docking at the same time. (J24.75.w2)
    • It was noted that this result was different from that seen in other experiments in which the clamp was applied across the whole scrotum and it was considered probable that that the area of uncrushed scrotal tissue provided undamaged nerve fibres in this region allowed nociceptive impulses from ischaemic scrotal tissue to be transmitted cranially. Other possible factors in the difference of results were the type of castrator used (Ritchey Nipper rather than Burdizzo) and the breed of lambs. (J24.75.w2)
  • A study compared the integrated cortisol responses (area under the cortisol-time concentration curve for four hours after the procedure) of lambs to castration and tailing using combinations of surgery, rubber rings and (for tail docking) a heated docking iron in lambs of four to five weeks old. The study concluded, based on the integrated cortisol response as a measure of acute distress, that surgical castration and/or tailing resulted in the greatest acute distress in the lambs, that tail docking with a ring caused less stress than ring castration alone or ring castration plus tailing (the later two causing similar levels of distress to one another), that tail docking with a docking iron or with a ring caused similar levels of distress, but with a shorter acute distress response with the docking iron than with rubber rings and that castration plus tail docking both with rubber rings, short-scrotum plus tail docking with rubber rings and rubber ring castration plus docking iron tailing produced similar levels of distress to one another. All lambs showed a transient increase in plasma cortisol level. In lambs castrated surgically (bottom third of the scrotum cut off with a sharp knife, testes drawn out using serrated tongs) and/or tail docked with a sharp knife, cortisol had not returned to pre-treatment levels by four hours after the procedure, whereas in other groups it had. It was noted that the lower response to tail docking with the heated docking iron may be related to destruction of nociceptors. [1991](J10.39.w2)
  • A study looked at the cortisol responses of lambs of about 40 days old to surgical castration and/or tail docking, and also tested whether handling for blood sampling affected the cortisol response. The study showed that cortisol responses were completed in approximately eight hours in all the lambs. Lambs of all groups showed a protracted cortisol response with levels returning to pre-treatment levels at 450 and 420 minutes in two groups (handled and blood samples every 15 minutes or not handled until 90 minutes, then every fifteen minutes respectively) and levels approaching but still significantly different from pre-treatment levels at 480 minutes in two other groups (handled from 240 minutes or only at 480 minutes). [1991](J10.39.w3)
  • A study looked at cortisol responses of lambs to tail docking by rubber ring, castration by rubber ring, and administration of ACTH from four hours after birth to seven days old in two breeds of sheep (Dorset and Scottish Blackface). In both breeds the integrated cortisol response was dependant on treatment (P<0.001), with least responses in control lambs, then (in order of increasing response) in tail docked, castrated and docked, and ACTH-injected lambs. In Scottish Blackface lambs there were no significant changes with age in response to control handling, tail docking or castration whereas in the Dorset lambs responses increased between four hours and one day old then decreased. In both breeds there was a significant (P<0.05 in Dorset, P<0.01 in Scottish Blackface) decrease in cortisol response to injection of ACTH between four hours and seven days of age. By expressing the cortisol response to noxious stimuli as a percentage of the response to a fixed dose of ACTH it was shown that in both breeds there were "marked increases in their apparent ACTH secretory responses to noxious stimuli during the first one to three days after birth", however it was further noted that "it would be premature to conclude that the distress caused by noxious stimulus increases during the first one to three days after birth." [1989](J21.46.w3)
  • A study compared the behavioural and cortisol responses of lambs of five- to six-days-old to castration and tail docking by standard rubber rings, smaller rubber rings, a combination of rings plus Burdizzo with the Burdizzo applied across the whole scrotum or tail just distal to the ring for ten seconds at each site, or Burdizzo alone, applied conventionally to each side of the scrotum across the spermatic cord for ten seconds each side, and across the whole width of the tail for three seconds. The study found that while all methods of castration and tail docking caused considerable acute pain, based on combined behavioural and cortisol measurements, the combined "ring plus Burdizzo" method produced least pain and the small rubber rings produce more intense pain than the standard rubber rings but lasting for a shorter period. [1995](J3.136.w3)
    • With the Burdizzo alone the main behavioural responses included decreased activity and abnormal postures, including statue standing and "dog-sitting", but few active behaviours such as foot stamping; the cortisol response peaked at a level at least twice of that seen in control handles lambs and was still raised at 180 minutes. With the combined method time spent in abnormal postures was not significantly different from that seen in Burdizzo-treated lambs but the time spent standing abnormally was less and no dog-sitting was seen, less time was spent lying in abnormal positions than in either of the rubber-ring groups, levels of active behaviours were similar to those seen in the control and Burdizzo groups and more time was spent in normal postures than in the other castrated groups; the increase in cortisol was smaller and of shorter duration than after any of the other castration methods and reduced to pretreatment levels by 48 minutes. With both rubber rings there were markedly more active behaviours and tail wagging, these being seen mainly in the first 42 minutes in the lambs castrated with the small rings and in the first 72 minutes with the standard rings, time spent in abnormal postures was greater than in control lambs and for standard rings was significantly higher than that seen with the Burdizzo or combined treatment. Lateral lying predominated with the small rings and included rolling, kicking etc., particularly in the first 12 minutes, while with the standard rings abnormal ventral lying, also sometimes with rolling and kicking, was predominant in the first 30 minutes. Active abnormal standing was seen rather than statue standing. The cortisol peak was higher and earlier with the smaller rings than with the standard rings but the difference was not statistically significant. [1995](J3.136.w3)
  • A study compared the acute cortisol response and wound healing in three- to six-week-old lambs castrated and tail docked by rings or by combined rings plus application of a Burdizzo castration clamp to the whole width of the scrotum just distal to the ring, for either six or ten seconds. Only a marginal reduction in cortisol response was seen with the combined method compared to rings alone but healing of the scrotal wounds were faster with the combined method. It was noted that flinching was observed in every lamb when the clamp was applied to the scrotum or tail and that this "would be a significant impediment to farmers adopting widely the ring plus clamp method." [2000](J24.78.w1)
    • Ring castration and docking produced a marked rise in plasma cortisol, significant (P<0.05) by 200 minutes, peaking at 60 minutes and returning to pre-treatment values by 170 minutes. Responses in the combined treatment groups were broadly similar, but the response peaked at 40 minutes in the lamps with 6 second clamp application and showed a plateau at 60 to 110 minutes in the lambs with 10 second clamp application. The only between-group significant difference was a lower cortisol level  (P<0.05) at 60 minutes in the lambs receiving the 10 second clamp and there were no significant differences in the integrated cortisol responses between groups. There was a trend for faster healing of the scrotal wounds in the lambs treated by the combined method, for example at four weeks after treatment, 8% versus 3% had progressed to a small star-shaped scar. [2000](J24.78.w1)
  • A study compared the behavioural and cortisol responses of lambs to castration and tailing by knife, rubber rings (castration or short scrotum), or (tailing only) heated docking iron. The study found that on the basis of the combined cortisol and behavioural responses, surgical castration and tail docking caused greater and more protracted pain than the other methods and should be avoided, but that ring castration or ring castration plus docking also caused distress and that "more benign alternatives" should be looked for. [1996](J10.44.w3)
    • With all methods the plasma cortisol level increased, then decreased to control values within 2.5 to 3.5 hours of the procedure, except in lambs castrated and/or docked with the knife. Following castration and/or tail docking with a knife, restless behaviours were not a feature but abnormal standing/walking, particularly "statue standing" was a major behaviour and this continued up to and beyond the end of the period of observation (four hours). With the rings, high levels of restlessness were seen in the first 30 to 45 minutes, most standing/walking was abnormal and lying was mainly abnormal and in short bouts, but all behaviours returned to control values within the four hours. Behavioural responses in lambs tail docked with a heated docking iron were generally similar in type to those in lambs docked with a knife, but lasted for a shorter time, reducing to normal values within the four hours, and the integrated cortisol response was at least 2.8 times less than in the lambs tail docked with a knife. It was noted that it was not possible to tell whether "restlessness" type behaviours or "abnormal standing/walking" indicated a greater amount of pain. [1996](J10.44.w3)
  • A study comparing the behavioural responses of lambs of three ages, (five, 21 and 42 days) to different castration methods (rubber ring, combined Burdizzo clamp and rubber ring, surgical) found that  all methods at all ages "produced changes in behaviour which could be interpreted as evidence for the presence of considerable pain during the first three hours after treatment." [1993](J21.55.w1)
  • A study used visual analogue scale (VAS) scoring for active behaviours, unresponsive behaviour and scrotal pain (on palpation) in association with cortisol measurements and mechanical threshold testing for quantification of pain responses associated with three different castration methods in mixed breed lambs of four to six days old. Active pain behaviours, which were virtually absent from control lambs, were seen in castrated lambs for up to three hours after castration; the highest scores were for ring castration, followed by the combined method, with the lowest scores for surgical castration. Looking at unresponsive behaviours, the pattern seen in ring or combined method castrates was similar to that of active pain behviours, while surgically castrated lambs showed higher levels of this behaviour than did control lambs for the whole eight hour observation period following castration. Looking at scrotal pain, in surgically castrated lambs this rose steadily to a peak by six hours then fell to pre-castration levels by 72 hours, while in those castrated by the other two methods, the initial rise was similar in pattern to that seen for active pain behaviours, but did not return to pre-castration levels in the 72-hour observation period. Integrated pain responses were significantly higher than those seen in control lams whichever castration method was used; the greatest integrated active pain behaviour was seen with ring castration and the least with the combined method. All castration methods caused rises in plasma cortisol and the rises were significant in ring and surgically castrated lambs at 15 minutes and in the rubber ring castrates at one hour, compared with controls; at eight hours no group had significantly higher cortisol, but at 24 hours a significantly higher level was seen in those castrated by the combined method, compared to all the other groups. Surgery or the combined castration resulted in a significant rise in the threshold response to a mechanical noxious stimulus compared to control lambs, while those castrated with rubber rings showed a slight rise then a slight fall in threshold. [1999](J21.66.w1)
  • A study of behavioural responses of lambs of two ages (one-week-old and four- to six-weeks-old) to rubber ring or combined rubber ring and Burdizzo (whole width of scrotum, 10 seconds) castration, found that in the three days following castration some behaviours which are considered normal in lambs were reduced, such as gambolling in one-week-old lambs (P=-.033) and lying in four- to six-week-old lambs (P= 0.0002). Postures considered abnormal, although sometimes seen prior to castration, were seen significantly more frequently (P=0.0025) in four- to six-week-old lambs following castration. Use of the combined method produced some reduction in these effects on behaviour, although the differences were not statistically significant. (J147.11.w1)
  • Lambs of eight weeks old castrated and tail docked by rubber rings showed a rise in mean plasma cortisol level to 50 minutes after ring application, which then declined slowly, remaining significantly higher than in control handled lambs from 20-180 minutes, to return to levels seen before the rings were applied by 210 minutes. Plasma noradrenaline concentrations increased markedly to 10 minutes after the rings were applied, remained at a high level until 30 minutes then returned to original levels by 60 minutes; mean concentrations were higher than in controls from 10 to 40 minutes. The rise in noradrenaline occurred during the onset of ischaemic pain. No rise in plasma adrenaline concentration was recorded; it was suggested this may be due to a lack of detection: the first blood sample was taken five minutes after ring placement and plasma catecholamines have a half-life of only one to two minutes, therefore the study may not have detected any immediate and short lived adrenaline response to placement of the rings. (J24.80.w2)

Rubber rings:

  • Application of rubber rings for tail docking and castration is simple, cheap and effective. However in lambs of all ages it produced considerable pain for more than an hour, as can be shown by hormonal (cortisol) and behavioural measurements. (J35.162.w1)
  • Several studies have shown that application of rubber rings "can cause pain sufficient to dominate the experience of the lamb for more than one hour." (J15.14.w3)
  • Following application of rubber rings to the scrotal neck of lambs for castration, vigorous afferent activity was recorded including activity from formerly silent units with receptive fields in the pampiniform plexus in particular. There was a rapid adaptation of the multi-unit discharge within 10 seconds followed by a discharge pattern decaying exponentially over 90 minutes and showing two components with inflections at approximately 90s and 16 min. Afferent activity initiated by application of rubber rings was shown to persist for periods in excess of 90 minutes; this time course is similar to that shown for behavioural and humeral changes in response to the same procedure. Neither standard nor smaller diameter rubber rings were effective in rapidly blocking slowly conducting afferent fibres in the superior spermatic nerve by neuronal pressure block. Intratesticular injection of local anaesthetic was shown to rapidly block afferent fibres running in the superior spermatic cord. (J287.19.w1)
  • A study using behavioural and cortisol responses to castration and tail docking of young lambs (five to six days old) with tight rubber rings indicate that the procedure caused "intense pain and distress for at least one hour." [1991](J21.51.w3)
    • Rubber ring castration and tail docking of five- to six-day-old lambs caused a significant rise in plasma cortisol level, peaking at approximately 30 minutes after the procedure, significantly raised (p<0.05) to at least 60 minutes and returning to pretreatment levels after 90 minutes. [1991](J21.51.w3)
    • Five- to six-day-old lambs castrated and tail docked by rubber rings showed significantly higher levels (p<0.05, compared to control handled lambs) of lateral recumbency (in the first hour) and of standing and walking (in the first 30 minutes and in the 120 to 180 minute period). Ventral lying was significantly lower than controls in the first 60 minutes and was higher in the 120-180 minute period. [1991](J21.51.w3)
  • In lambs of three weeks old, cortisol responses were similar after Burdizzo clamp, a powered castration clamp or rubber ring combined with a Burdizzo clamp applied across the whole scrotum for ten seconds; the cortisol response was most prolonged after use of the powered castrator. Behavioural responses with the three methods were similar to one another with significant increases (compared to control handled lambs) in time spent in abnormal postures (P < 0.01), particularly statue standing with the Burdizzo or powered clamp and abnormal lying for the combined ring and Burdizzo method, significantly greater amounts of time spent trembling (P <0.05), mainly in the first 60 minutes after castration, and significantly greater time showing active behaviours (restlessness, easing quarters and total active behaviours). [1997](J35.153.w1)
  • Rubber ring castration caused significantly more (P < 0.01) combined active pain related behaviours, abnormal ventral lying, lateral lying and total abnormal lying and total abnormal postures, less normal ventral lying than in control lambs, and also significant plasma cortisol responses, peaking at about 60 minutes after castration and returning to control values at about 120 minutes. [1998](J35.155.w1)
  • Rubber ring castration and tail docking caused consistent active behaviours indicative of discomfort (e.g. restlessness, easing the quarters, tail wagging not associated with sucking, rolling, vocalisation not associated with suckling, turning the head to an abnormal position, generally to look at/lick the scrotum) in neonatal lambs, with scores being significantly (P<0.01) greater than those for control handled lambs, and with castration plus tail docking of male lambs producing a significantly (P<0.01) greater effect than tail docking alone in ewe lambs. (J3.149.w3)

Rubber ring plus Burdizzo:

  • Several studies have indicated that combining use of rubber rings with crushing the innervation to the testes, scrotum and tail using a clamp (Burdizzo) reduces the duration of pain, compared to use of rubber rings alone, although the immediate pain at the time of application is increased. (J3.136.w3, J21.55.w1, J35.162.w1, J35.155.w1, J290.24.w1)

Evidence from use of local anaesthesia:

"Behaviour elicited by treatment can be validated as measures of noxious sensory input if effective local anaesthesia returns levels close to those seen in control animals." (J10.47.w3)

  • Administration of local anaesthesia prior to rubber ring castration and tail docking in lambs eliminates the behavioural signs and the plasma cortisol changes which are normally seen following castration and tail docking, indicating that the behavioural and cortisol responses are due to pain. [1991](J21.51.w3)
  • Both the testes and the scrotum contribute noxious sensory input following ring castration but the cortisol response to ring application can be abolished by injection of local anaesthetic into the neck of the scrotum or into both testes before application of the rings. Injection into the spermatic cords reduced the cortisol response but this reduction was not significant. [1997](J10.45.w3)
  • Pre-treatment with local anaesthetic reduced levels of active pain behaviours, unresponsive behaviours and scrotal pain on palpation measured by VAS following ring or combined ring and Burdizzo clamp (full scrotal width) castration to levels similar to those seen in control lambs. [1999](J21.66.w1)

Evidence from administration of naloxone:

  • A study indicated that endogenous opioids do reduce pain in young lambs following castration and tail docking but have only a slight effect. Administration of intravenous naloxone (opiate antagonist) prior to rubber ring castration and tail docking in lambs resulted in the treated lambs reaching a higher plasma cortisol concentration, from a lower starting level, than seen in lambs subjected to castration and tail docking alone, although this difference was not significant. There was an increase in lateral (abnormal) lying behaviour in the naloxone treated lambs in the first hour after castration; this was significant (P<0.05) only in the 30 to sixty minute period. Some lambs showed increased teat seeking and sucking, which may be an additional mechanism for alleviation of acute pain and distress. [1991](J21.51.w3)

Evidence for chronic pain:

  • When tails from docked and undocked lambs were examined post mortem, obvious swelling was visible in the distal nerve stump of three of six docked lambs but not in any undocked lambs. Histological examination revealed terminal neuromata at the distal ends of the main coccygeal nerve trunks in two docked tails and complex neuromata (multiple, discrete irregularly distributed nerve bundles within connective and scar tissue) in two other docked tails. It was suggested that the presence of the neuromata suggested the possibility of chronic pain or increased sensitivity remaining "long after amputation." [1992](J21.52.w1)
  • Lambs castrated by rubber ring at two days old showed behaviours such as licking directed towards the affected area, and movements of the hind limbs and tail, "which may be considered as evidence of chronic pain". The incidence of such behaviours was greater in lambs castrated at 42 days, and lesions which developed were also more severe in the older lambs. [2000] (J35.160.w1)
    • A study on lambs castrated and tail docked by rubber ring alone, or with local anaesthesia or combined with Burdizzo clamp (across the whole scrotum) at less than two days old, found that an inflamed lesion developed at the site of the rubber ring on all lambs with no significant effect of method on maximum lesions score, although the combined method did cause the lesion to develop and to heal more quickly. All tails but one had dropped off by 28 days. The time taken for the scrotum to drop off was not significantly affected by method (although only 20% had dropped off by 28 days in the ring group compared to 50% in the other groups) nor was the maximum lesion width or maximum lesion score; the time to maximum lesion width was lower for the lambs castrated with the combined method. Pus developed at the scrotal site in 35% of lambs and at the tail in 40% of those given local anaesthetic or the combined method but not in any lambs in which the rubber ring was used alone. Behaviourally (comparing ring castrated, ring castrated with local anaesthetic, and control handled lambs), in lambs castrated by rubber rings there were significantly higher incidences of the active behaviours foot stamping, kicking and tail wagging and combined (foot stamping, kicking, easing quarters, scratching quarters and tail wagging) than in control handled lambs or those given local anaesthetic, and there was a significantly higher incidence (compared to control handled lambs) of head turning to and licking of the inside hind leg and scrotum and although this behaviour generally correlated only poorly with lesion severity it was seen at highest incidence at the same time as the most severe lesion score, for the two lambs showing the highest incidence of this behaviour. Playing on a box was reduced by half in ring castrated lambs compared to handled controls and those given local anaesthetic, and gamboling was also lower, but the differences were not significant. Ring castrated lambs also showed higher incidences of abnormal lying postures, abnormal standing and lying idling, and fewer normal standing and play postures than handled lambs or those given local anaesthetic prior to ring application. There were no effects of treatment on liveweight gain. [2000] (J35.160.w1)
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Suggested methods of pain prevention

Age considerations:
  • A study of ring or ring plus Burdizzo clamp or surgical castration and tail docking concluded that acute pain was demonstrated at all ages. There were "no substantial differences" between the behavioural responses to combined ring plus Burdizzo clamp castration in lambs of five, 21 and 42 days of age, but surgical castration was more painful in lambs of five days old than in older lambs, while older lambs reacted more to rubber rings than did younger lambs (more restlessness and more abnormal lying). (J21.55.w1)

Use of least painful methods:

Cautery for tail docking:

  • Severing the tail by cautery can limit pain input from the stump; this may be due to destruction of pain receptors in the burnt tissue. (J10.39.w2, J10.48.w4)
  • Lambs of three weeks old, tail docked by use of a heated docking iron, showed an increase in trembling compared to handled control lambs but did not show significant increases in other behaviours indicative of pain (active behaviours or abnormal postures) not did they show a significantly greater cortisol response than control lambs. [1997](J35.153.w2)
    • Use of a heated docking iron for tail docking, which may be effective in reducing pain at and in the few hours after tail docking, may delay healing and lead to chronic infections and predisposition to fly strike. [1997](J35.153.w2)

Physical methods which obstruct transmission in pain nerve pathways or which disable pain receptors by preventing blood flow, may potentially reduce distress due to tail docking or castration. 

  • Application of a clamp damages the nerves in clamped tissues and interrupts nerve transmission from tissues distal to the crush line. When each cord is crushed separately there is an immediate barrage at the time of application, which subsides, with cessation of pain impulses from the testes and scrotum, but impulses may continue from nerves in the medial parts of the scrotum which have not been crushed. On the other hand if a full-width crush is applied then transmission of impulses from the testes and from all scrotal tissue distal to the crush site is obstructed. This can reduce the ischaemic pain occurring with ring castration of young lambs, and may reduce pain if used in association with ring tail docking. [2000](J10.48.w4) 
  • If a ring is used alone for castration or docking then distress is limited once the hypoxia/anoxia in the tissues distal to the ring disables pain receptors in that tissue. [2000](J10.48.w4)
  • In lambs, surgical castration in four- to six-week-old lambs produces the highest integrated cortisol response, about twice that of ring castration and tail docking. [2000](J10.48.w4)
  • Clamping alone, for 10 seconds on each cord, at 4 to 8 weeks old, produced a integrated cortisol response of 165 to 170% of that seen with ring castration and tail docking. [2000](J10.48.w4)

Short scrotum:

  • Short scrotum castration in lambs of 28 to 64 (mean 43) days old resulted in a significantly lower peak acute cortisol response than the response seen with ring castration. The integrated cortisol response was also lower, although the difference was not significant. The marginal difference may be due to the noxious stimulus from the scrotum being more important than noxious stimuli from the testes in production of the acute cortisol response. [1997](J10.45.w3)
  • Short-scrotum castration and ring tail docking did not have a significant benefit over ring castration and docking as measured by integrated cortisol response. [2000](J10.48.w4)

Tight ring: 

  • Castration and tail docking with a tight ring in one-week-old lambs resulted in an integrated cortisol response about 70-85% of that seen with ring castration and tail docking. [2000](J10.48.w4)

Ring plus Burdizzo clamp across the whole scrotal width:

"If the actual clamping procedure could be made less painful to the lamb, this method is likely to be the least distressing to the lamb." [1999](J21.66.w1)

It has been "well established" that this combined method "drastically reduces the pain response in the first three hours compared to using the ring alone." The combined method may also reduce pain in the three days following castration. (J147.11.w1)

  • In one-week-old lambs, castration and tail docking by rubber rings in combination with clamping applied for 10 seconds across the whole width of the scrotum and across the tail, immediately after the rings were applied, reduced the integrated cortisol response to 30% or less of that seen when rings were used alone. However, clamp application for a shorter time (six seconds) following ringing produced a smaller reduction in cortisol response in lambs of this age (to about 70-85% of that seen with ring castration and tail docking alone) while clamping full-width for 10 seconds in three-week old lambs, or clamping on each cord in lambs of three to eight-weeks old, did not have a significant effect on the integrated cortisol response. [2000] (J10.48.w4)
  • In 3- to 6-week-old lambs there was no benefit in reduction of acute pain, as measures by cortisol response, and it was noted that flinching was observed in every lamb when the clamp was applied to the scrotum or tail and that this "would be a significant impediment to farmers adopting widely the ring plus clamp method." [2000] (J24.78.w1)
  • A study in which behavioural responses to rubber ring, rubber ring plus Burdizzo clamp (across the whole scrotum) and surgical castration were compared in lambs of five, 21 and 42 days, concluded that rubber rings produced more acute pain than either of the other methods. [1993] (J21.55.w1)
    • When a Burdizzo clamp was applied across the whole scrotum for six seconds after application of rubber rings, in some but not all lambs abnormal behaviour was reduced, compared to those in which rubber rings were applied without the clamp. Significant reductions were noted in restlessness, time spent lying laterally and total abnormal behaviours. It was considered possible that six seconds was not an optimal time period for application of the clamp and that a longer period (ten seconds) might be effective more consistently. Destruction of at least part of the afferent innervation is thought to be responsible for the decrease in pain responses with the combined method. [1993] (J21.55.w1)
  • Application of a powered bloodless castrator clamp across the whole scrotum immediately after rubber ring application in five- to eight-day old lambs, reduced peak cortisol responses to rubber ring castration by 50% (P < 0.01), reduced active behavioural responses by 80% (P < 0.01) and reduced time spent in abnormal postures by 68 (P <0.01). [1998] (J35.155.w1)
  • Application of a powered bloodless castrator clamp across the whole tail immediately after rubber ring application in five- to eight-day old lambs, reduced peak cortisol responses to rubber ring tail docking by 44% (P >0.05), reduced active behavioural responses by 80% (P < 0.01) and reduced time spent in abnormal postures by 56% (P <0.01). [1998] (J35.155.w1)
  • Combined Burdizzo clamp with rubber ring castration reduced the time taken for the tail and scrotal lesions to heal, compared with rubber rings alone, which may be beneficial. [2000](J35.160.w1)
    • A study on lambs castrated and tail docked by rubber ring alone, or with local anaesthesia or combined with Burdizzo clamp (across the whole scrotum) at less than two days old, found that an inflamed lesion developed at the site of the rubber ring on all lambs with no significant effect of method on maximum lesions score, although the combined method did cause the lesion to develop and to heal more quickly. All tails but one had dropped off by 28 days. The time taken for the scrotum to drop off was not significantly affected by method (although only 20% had dropped off by 28 days in the ring group compared to 50% in the other groups) nor was the maximum lesion width or maximum lesion score; the time to maximum lesion width was lower for the lambs castrated with the combined method. Pus developed at the scrotal site in 35% of lambs and at the tail in 40% of those given local anaesthetic or the combined method but not in any lambs in which the rubber ring was used alone. [2000] (J35.160.w1)
  • Combined ring plus Burdizzo (across the whole scrotal width for 10 seconds) produced some reduction in effects on behaviour seen in the three days following ring castration in one-week-old and in four to six-week old lambs, although the differences were not statistically significant. (J147.11.w1)
  • Combining ring castration with application of a bloodless castrator, modified from the "Ritchey Nipper" (Ritchey), significantly reduced abnormal behaviour scores in lambs of less than two days old, compared to application of rings alone, and also significantly reduced VAS scores given by observers; there were increases in lying with the hindlegs partially extended, and statue standing, with this combined method. Reductions in VAS scores were also seen for ewe lambs given the combined treatment in comparison to those tail docked with rings alone. Shepherds noted that the use of the combined method allowed lambs to be moved from the lambing pens earlier. Tail and scrotal lesions healed more quickly than with rings applied alone. (J3.154.w2)

Ring plus castration clamp across each spermatic cord:

  • Combining ring castration with crushing with a clamp across each of the two spermatic cords, for one, five, or 10 seconds, did not reduce the cortisol response compared with that seen with ring castration alone. [1997](J10.45.w3)

Burdizzo clamp castration:

  • Burdizzo clamp castration, with application of the clamp to each of the two spermatic cords individually for one or ten seconds, leaving intact tissue between, produced mean cortisol responses no less than those seen with ring application. The integrated cortisol response following application of the clamp for 10 seconds on each cord was higher (p<0.05) than that seen with ring castration. It was suggested that use of rings would be preferable to the conventional use of a clamp on each spermatic cord. [1997](J10.45.w3)
  • Plasma cortisol concentration rises more rapidly following application of a Burdizzo clamp to each spermatic cord for castration than with rubber ring application. This probably reflects barrages of afferent neural impulses during and after the clamp crushing the spermatic and scrotal nerves in contrast to the ring application resulting in progressive hypoxia with an associated slower onset of noxious activity. A similar pattern of decrease in cortisol seen with ring or ring plus clamp is probably due to nociceptors distal to the ring becoming progressively disabled from about 60 minutes due to the developing hypoxia/anoxia of the tissues distal to the ring. [1997](J10.45.w3)

Surgical castration:

  • This appears to be the most painful method of castration in lambs and should be avoided.
    • A study using visual analogue scale (VAS) scoring for active behaviours, unresponsive behaviour and scrotal pain (on palpation) in association with cortisol measurements and mechanical threshold testing for quantification of pain responses associated with castration by three methods, confirmed surgical castration as more painful than ring or combined ring plus Burdizzo clamp (full scrotal width) castration. The "integrated" behavioural pain scores and cortisol response were as high as those seen with rubber ring castration while a prolonged period of hypoalgesia was demonstrated as intense as that seen with the combined castration method. (J21.66.w1)

Site of ring application for tail docking:

  • It has been observed that the degree of behavioural responses to rubber ring tail docking can show marked variations between individuals. In a study of this observation, rings were applied to the tails of lambs, then in the lambs which showed only limited behavioural responses (16% of lambs) the rings were removed, and then re-applied two days later at the same or a different site on the tai. The study showed that the responses varied depending on the site of ring application. Those in which the ring was replaced at the same site showed similar responses to the responses seen initially, while those in which the ring was placed at a different site showed a seven-fold increase in active behaviours compared to the first application (P=0.02) and also an increase in the time spent in abnormal postures from zero to 13 minutes (approaching significance, P=0.06). It was not possible to tell exactly where, anatomically, the rings had been placed but it was suggested that the low responses may be associated with placement in the intervertebral space where speed of conduction block may occur due to mechanical deformation of the nerve trunks by the ring. (J35.164.w1)

Pharmacological alleviation of pain

  • NOTE: In the UK, anaesthesia is a legal requirement for castration of sheep over three months of age, under the Protection of Animals (Anaesthetics) Act 1954 (as amended). (B359.App8.w30, D158)

General anaesthesia:

  • This renders an animal unconscious thus pain is not experienced (J4.221.w2, J10.48.w4). However, it is not a practical option for use in routine procedures carried out on large numbers of farm animals. (J10.48.w4)
  • This is rarely, if ever, used for lamb castration. (J15.14.w3)
  • General anaesthesia is time consuming, requires skill, and is in itself hazardous; it is not generally appropriate in the farm situation. (D153)
  • General anaesthesia (halothane, 1 to 2% in 100% oxygen) reduced levels of active pain behaviours measured by VAS following combined ring and Burdizzo clamp (full scrotal width) castration but did not significantly reduce these behaviours following ring or surgical castration (although a trend towards reduction was noted). Unresponsive behaviours were increased in all lambs (including control handled lambs) following use of general anaesthesia; the integrated unresponsive response was significantly greater in surgically castrated lambs than in control lambs. There was no effect of general anaesthesia on scrotal pain scores. General anaesthesia had little effect on plasma cortisol responses compared to no anaesthesia; levels at 60 minutes were significantly higher in ring or surgically castrated lambs than in controls. Without anaesthesia, levels were significantly higher than in control lambs for ring castrated lambs at 15 and 60 minutes, for surgically castrated lambs at 15 minutes and for combined ring and clamp castrated lambs at 24 hours. The mechanical nociceptive threshold was significantly raised following surgical or combined ring plus Burdizzo castration, while ring castration caused a slight rise followed by a slight fall, without reaching significance. General anaesthesia significantly raised the threshold following surgical castration but not following the other castration methods [1999] (J21.66.w1)

Use of local analgesics:

  • Use of local anaesthetic drugs may be an effective way to eliminate acute pain produced by castration and tail docking, whatever the method of castration and tail docking, "providing all the nerves involved are exposed to an appropriate local anaesthetic for a sufficient time." (J15.14.w3)
    • Intratesticular injection of local anaesthetic has been shown to rapidly block afferent fibres running in the superior spermatic cord. (J287.19.w1)
    • Either about 2 mL of local anaesthetic solution may be injected under the scrotal skin and a further 3-5 mL into each spermatic cord; or 3-5 mL of local anaesthetic solution may be injected into each testis, with a little injected subcutaneously as the needle is withdrawn. (B359.App8.w30)
      • This provides analgesia after about 10 minutes. (B359.App8.w30)
    • Provision of local analgesia without using a syringe and needle would be preferable for ease of use, reduced pain associated with administration, and reduced risk of infection. (D153)
    • Injection of local anaesthetic into the testes/scrotum and/or tail, in large numbers of lambs in typical farm conditions, would involve a risk of introduction of infection in some lambs. (P61.53.w1)
    • N.B. It is also important to ensure that the procedure is carried out while the local anaesthetic is still active. (V.w5, V.w6)
  • Injection of local anaesthetic blocks transmission of impulses in the treated nerves for the duration of action of the local anaesthetic drug used. With lidocaine the duration of action is about two hours, with bupivacaine about three hours or longer. (J10.48.w4)
    • Duration of action is extended if clearance of anaesthetic is prevented by obstruction of blood flow by a ring. (J10.48.w4)
  • Sites for injection of local anaesthetic for castration include: (J10.48.w4)
    • the neck of the scrotum;
    • both spermatic cords;
    • both testes;
    • combinations of these (scrotal neck and spermatic cords or scrotal neck and spermatic cords and testes). (J10.48.w4)
  • Sites for injection of local anaesthetic for tail docking: (J10.48.w4)
    • injected subcutaneously around the tail;
      • This may be more painful than the tail docking procedure. (D153)
    • administered with a high pressure needleless device
    • spray applied onto the skin around the tail. (J10.48.w4)
  • For castration by rubber rings local anaesthetic should be applied before rubber rings are applied, in order to allow rapid transport of the drug to the spermatic veins and lymphatics. If applied after the ring has been applied then distribution, which occurs by diffusion, is slower and it may take considerably longer to block all the afferents from the testis. Once the ring is applied the local anaesthetic should, since the blood vessels are occluded, remain in the testes and scrotum and maintain local anaesthesia until after cessation of action of the afferents. (J15.14.w3)
  • For surgical castration or tail docking there is the possibility of prolonged pain, and local anaesthetic will dissipate, not be retained in the local tissues, therefore a local anaesthetic with as long a period of action as possible should be used, particularly since with some methods pain may be prolonged. (J15.14.w3)
  • Scientific studies have shown the following effects of application of local anaesthesia: 
    • Administration of local anaesthesia prior to rubber ring castration and tail docking in lambs of five to six days old eliminated the behavioural signs and the plasma cortisol changes which were seen following castration and tail docking without analgesia, for a period of four hours of observation following castration and tail docking. [1993](J21.51.w3)
      • Abnormal lateral lying behaviour (lying on the side in an abnormal posture), seen after rubber ring castration and tail docking with rubber rings, was eliminated when local anaesthesia was administered prior to the procedure being carried out, and other signs of pain (bleating, kicking, tail wagging, turning the head and restlessness) were absent; in general behaviour was similar to that of control lambs and to those which had been given local anaesthetic without being castrated and docked. Cortisol response was reduced also: there were no significant differences in plasma cortisol levels between control handled lambs, those given local anaesthesia alone and those given local anaesthesia then castrated and docked, while there was a significant rise (P<0.05) in lambs castrated and docked without local anaesthesia. [1993](J21.51.w3)
    • For Burdizzo clamp castration of lambs of 28 to 64 days old (mean 43 days), with the clamp applied to each cord individually for 10 seconds, local anaesthetic injected into either the spermatic cords or the scrotal neck prior to the procedure significantly reduced the integrated cortisol response, however responses were still similar to those seen following ring castration without local anaesthetic. [1997](J10.45.w3)
    • Injection of local anaesthetic into the scrotal neck or into both testes effectively abolished the acute pain-induced distress to ring castration as measured by cortisol responses. It was noted that in farm conditions testicular application would be preferable to scrotal neck injection as it is more straightforward for effective application by relatively unskilled personnel. [1997](J10.45.w3)
    • Injection of the local anaesthetic agent bupivacaine into the testes (0.25%, 1 to 2 minutes prior to castration) before Burdizzo or combined rubber ring and Burdizzo castration in three-week-old lambs provided some analgesia within two minutes but was not reliable at this time. There were significant (P < 0.05) reductions in average peak plasma cortisol levels, time spent trembling and time spent in abnormal postures with the use of local anaesthetic prior to either method of castration. [1997](J35.153.w1)
    • Subcutaneous injection of 1.0 mL 0.25% bupivacaine subcutaneously, across the dorsal and ventral surfaces of the tail (0.5 mL each) administered by introducing a needle across the width of the tail and injecting as the needle was withdrawn, one to two minutes prior to tail docking by rubber ring, significantly reduced times spent in active behaviours (P < 0.01), abnormal lying postures (P < 0.01), abnormal standing postures (P < 0.05) and total abnormal postures (P <0.05) and also significantly reduced cortisol responses. This method of analgesia prior to combined rubber ring and Burdizzo (across the whole tail for 10s) also significantly (P <0/01) reduced abnormal postures, and when given prior to docking by heated docking iron significantly (P <0.05) reduced "statue standing" with trembling. [1997](J35.153.w2)
    • Use of an analgesic freeze spray (Ralgex, Beecham) on the dorsal and ventral surfaces of the tail a few seconds prior to rubber ring tail docking at the same position as spray application, significantly (P < 0.01) reduced the mean cortisol response and also significantly reduced active pain behaviours (P < 0.05) but did not reduce times spent in abnormal postures (lying, standing or overall). [1997](J35.153.w2)
    • Application of local anaesthetic by use of a needleless injector immediately after application of rubber rings is effective in reducing pain due to rubber ring castration and tail docking. There are practical limitations associated with the design of the injector (e.g. difficulty in injecting the tail, frequent reloading required) and injection about five minutes prior to castration would allow more (most) of the pain associated with these procedures to be eliminated. [1998](J35.155.w1)
      • Application of local anaesthetic (0.2 mL of 2% lidocaine with adrenaline per site) by injection into the scrotal neck at the site of ring application, either with a needle and syringe or a high-pressure needleless injector (Syrijet, Keystone Industries), in five- to eight-day old lambs, reduced peak cortisol responses to rubber ring castration by 50% (P < 0.01), reduced active behavioural responses by 64% (P < 0.01) and reduced time spent in abnormal postures by 59% (P <0.01). Application of local anaesthetic into the testes was less effective than application into the scrotal neck (P< 0.05), abnormal lying behaviours reduced respectively by 46% versus 71%. [1998](J35.155.w1)
      • Application of local anaesthetic (0.2 mL of 2% lidocaine with adrenaline per site) into either side of the tail on the dorso-lateral aspect, either with a needle and syringe or a high-pressure needleless injector (Syrijet, Keystone Industries), in five- to eight-day old lambs, immediately before rubber ring application reduced peak cortisol responses to rubber ring tail docking by 60% (P <0.01), reduced active behavioural responses by 80% (P < 0.01) and reduced time spent in abnormal postures by 56% (P <0.01). [1998](J35.155.w1)
    • Injection of local anaesthetic into the scrotal neck immediately before castration and tail docking by rubber rings can significantly reduce, although not eliminate, the cortisol response (and therefore presumably the pain) associated with these procedures. (J24.77.w1)
      • Injection of local anaesthetic into the neck of the scrotum (1.0 mL into the anteriomedial surface and 0.5 mL into each lateral surface) five to 10 seconds before rubber ring castration and tail docking significantly reduced the plasma cortisol response to ring application from 20 to 150 minutes after ring application and the integrated cortisol response. However the cortisol response was still significantly higher than in control handled lambs. Local anaesthetic injection into the testes immediately prior to rubber ring castration and tail docking caused only a slight reduction in cortisol response, not significant at most times although there was a significant reduction in the peak cortisol at 60 minutes. [1999](J24.77.w1)
    • Local anaesthetic application appears to be effective in reducing pain associated with ring castration or combined ring and Burdizzo clamp (full scrotal width) castration but not in reducing the long-term post-operative pain associated with surgical castration in lambs. [1999] (J21.66.w1)
    • Pre-treatment with local anaesthetic reduced levels of active pain behaviours, unresponsive behaviours and scrotal pain on palpation measured by VAS following ring or combined ring and Burdizzo clamp (full scrotal width) castration to levels similar to those seen in control lambs. In surgically castrated lambs use of local anaesthetic reduced active pain behaviours to a level not significantly different from that of control lambs but did not affect unresponsive behaviour, while scrotal pain on palpation was significantly increased. Local anaesthesia reduced the rise in cortisol level seen with all three methods of castration so that levels were no longer significantly higher than those seen in control lambs. Without anaesthesia levels were significantly higher than in control lambs for ring castrated lambs at 15 and 60 minutes, for surgically castrated lambs at 15 minutes and for combined ring and clamp castrated lambs at 24 hours. The mechanical nociceptive threshold was significantly raised following surgical or combined ring plus Burdizzo castration while ring castration caused a slight rise followed by a slight fall, without reaching significance; pre-treatment with local anaesthetic abolished the rise in thresholds seen with the combined castration but did not significantly change the response to surgical castration. [1999] (J21.66.w1)
    • Injection of local anaesthetic prior to rubber ring castration in two-day-old lambs resulted in earlier healing of the scrotal lesion and appeared to prevent the increase in abnormal behaviours and activities which were seen in lambs not given local anaesthetic, although it was noted that there may have been an earlier peak of abnormal activity (due to earlier development of lesions) not recorded. [2000](J35.160.w1)
    • Application of local anaesthetic (0.3 mL of lidocaine 20mg/mL into each testis prior to ring placement, and an additional 0.3 mL under each ring immediately after ring placement) significantly reduced abnormal behaviour scores in lambs of less than two days old, compared to application of rings without local anaesthetic, and also significantly reduced VAS scores given by observers. Reductions in VAS scores were also seen for ewe lambs given local anaesthesia in comparison to those tail docked without any analgesia. Shepherds noted that the use of local anaesthetic allowed lambs to be moved from the lambing pens earlier. Slightly higher growth rates were recorded also (P=0.044) at follow-up after 24-44 days. Tail and scrotal lesions healed more quickly than with rings applied alone. (J3.154.w2)

Use of NSAIDs:

  • NSAIDs are administered by intravenous or intramuscular injection for systemic distribution. They do not block the barrages of pain impulses associated with the initial tissue injury but they are able to act on damaged tissues not accessible to nerve blockade, and their effect is generally longer lasting than that of local anaesthetic drugs. (J10.48.w4)
  • There are practical problems regarding mass administration of analgesics, including withdrawal periods. (D153)
  • Scientific studies have shown the following effects of NSAIDs: 
    • Intramuscular administration of an NSAID has been shown to reduce pain associated with castration, indicated by reduced cortisol response and by reduction in two of three types of behavioural signs of pain. [1997](J35.153.w1)
      • The NSAID diclofenac (1.5 mg/kg Voltarol, Geigy) given 20 minutes prior to Burdizzo castration in three-week-old lambs, significantly reduced the peak plasma cortisol response to the procedure and also significantly reduced two of the behavioural signs of pain, the time spent trembling and that spent showing abnormal postures. The main reduction in abnormal postures occurred from 12 minutes after castration, indicating that the NSAID may have been acting mainly as an anti-inflammatory and reducing inflammatory pain rather than the initial pain directly resulting from the crushing action of the Burdizzo. [1997](J35.153.w1)
        • It was noted that other NSAIDs might be more effective than diclofenac. [1997](J35.153.w1)
    • Intramuscular administration of an NSAID has been shown to reduce the cortisol response, and therefore probably the pain, associated with tail docking. [1997](J35.153.w2)
      • The NSAID diclofenac (1.5 mg/kg Voltarol, Geigy) given 20 minutes prior to rubber ring tail docking in three-week-old lambs, significantly (P < 0.01) reduced the mean cortisol response. Some behavioural signs normally indicative of pain were increased compared with lambs docked with rubber rings without pain relief; it was considered that this might have been an artifact due to large variations between lambs, with three of the lambs docked by rubber ring alone showing only very limited behavioural responses while only one of the diclofenac treated group showed the limited responses. [1997](J35.153.w2)
    • Subcutaneous administration of the NSAID carprofen at 0.5 mg/kg subcutaneously did not affect active pain behaviours in response to tail docking or castration and tail docking in neonatal lambs. carprofen
      • The NSAID carprofen (Zenecarp for calves, C-Vet) at 0.5 mg/kg subcutaneously 30 minutes prior to castration and tail docking of neonatal lambs did not significantly reduce active pain behaviours in these lambs compared to lambs not given analgesia. Possible reasons given for the lack of effect were insufficient dose, insufficient time for the drug to be absorbed and reach therapeutic concentrations, or lake of effect on NSAIDs on ischaemic pain. [2001](J3.149.w3)
    • Oral dosing with 26 mg/kg aspirin at the time of tail docking did not effectively reduce pain-related behaviours in the first 60 minutes after tail docking, in lambs tail docked using rubber rings at three to six weeks old , although some suggestion of effect (reduced restlessness) had been seen in a pilot study. (J288.71.w1)
      • It was considered possible that the dose was inadequate or that using only behavioural measurements of pain was not sufficient to detect any analgesic effect. (J288.71.w1)

Use of epidural anaesthetic:

  • Caudal epidural analgesia, with injection at the first intercoccygeal space, may be used for alleviation of pain associated with tail docking. (J10.48.w4, J15.14.w3)
  • This is not practical for general use as it "is a technically difficult procedure which can only be done by a veterinary surgeon" and while it could theoretically be taught to farmers, there would be a considerable risk of infection being introduced into the spinal canal with mass use under farm conditions. (D153)
  • A study successfully carried out epidural injection in 88 six-week-old lambs under field conditions without any resultant spinal meningitis or other untoward sequelae noted in the four months following the injections. "This study has indicated that epidural injection in young lambs is a safe and practical procedure that can be performed under field conditions." However, the study also found that epidural injection of 0.015 mg/kg or 0.03 mg/kg xylazine did not provide analgesia for castration using rubber rings. (J304.17.w1)
  • Epidural anaesthesia (0.5 mL of 0.25% bupivacaine, injected into the sacro-coccygeal space one to two minutes prior to tail docking) before tail docking by rubber ring, significantly reduced active pain behaviours (P < 0.01) and time spent in abnormal lying postures (P < 0.05) but reductions in time spent in abnormal standing postures and total time spent in abnormal postures were not significant. The mean plasma cortisol response was also significantly reduced. However, based on level of paralysis of the tail and responses of individual lambs, it appeared that effective epidural anaesthesia was not always achieved, probably due to failure to inject epidurally in some individuals. (J35.153.w2)

Use of suckled sucrose:

  • In human infants and in neonatal rodents, suckling of sucrose by the infant/neonate has been shown to be effective for analgesia in transient pain (e.g. heel-lancing) and (in rodents) in models of more persistent pain. However, a study on newborn lambs found no effect of suckled sucrose of active pain behaviours in neonatal lambs subjected to castration and tail docking or tail docking alone. (J3.149.w3)
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Reasons why adequate pain relief is not always provided

Reasons why adequate pain prevention may not be provided are described in detail in: Reasons for Failure to Provide Pain Relief. In brief, these include:
  • Attitudes towards pain in animals;
  • Tradition;
  • Failure to recognise pain;
  • Failure to recognise the importance of the adverse effects of pain;
  • Concern about removing possible protective effects of pain [this concern is generally excessive];
  • Concern that providing pain relief may itself stress the animal and have a negative impact on it;
  • Concern that treating pain may interfere with diagnosis;
  • Lack of information about analgesics;
  • Concern about toxicity and side-effects of analgesics;
  • Concerns about the safety and legislative controls associated with some analgesics such as opiates;
  • Economic and practical considerations.
Specific published reasons for failure to provide pain relief for lamb castration and tail docking are indicated below.

Failure to recognise pain/perception of pain:

  • It is suggested that there may be poor perception by shepherds of the pain associated with castration by rubber rings, since the pain responses are not apparent immediately at the time of ring application but in the hours after this. (J3.154.w2)
  • Shepherds may be reluctant to use the combined ring plus bloodless castrator (across the whole scrotum) method of pain reduction because they dislike applying the castrator, particularly to the tail (application does cause a short, sharp pain). (J3.154.w2)
    • Shepherds may not be aware of the reduced pain behaviours in the hours following the combined method, compared to the use of rings alone. (J3.154.w2)

Concerns about the safety and legislative controls associated with some analgesics such as opiates:

  • In many countries injection of local anaesthetics by farmers, rather than by veterinarians or under veterinary supervision, is illegal. (J24.77.w1)

Economic and practical considerations:

  • Use of local anaesthesia is costly in terms of the requirement to handle the lambs twice, once to administer the local anaesthetic and a second time to carry out the castration/tail docking, after an interval to allow the local anaesthetic agent to take effect. [1997](J35.153.w1)
  • Methods of local anaesthetic administration which have been shown to be effective for abolition of pain but require multiple injections are not likely to be acceptable for routine use. [1997](J35.153.w1)
  • Epidural anaesthesia for tail docking is effective if carried out correctly, but requires a veterinary surgeon for the administration and may not be carried out reliably (i.e. correct epidural injection may not be achieved) in field conditions. [1997](J35.153.w2)
  • Use of a heated docking iron for tail docking, while it may decrease pain, involves some risk of burning and of fire, and requires the use of two methods if also castrating (since this is useful only for tail docking). [1997](J35.153.w2)
  • Administration of a NSAID would be more practical if it could be shown that application at the same time as castration/tail docking was effective, as this would allow the lambs to be handled only once. [1997](J35.153.w1)
  • For better practical application a local anaesthetic is required which can quickly produce analgesia and preferably does not require injection by needle. [1997](J35.153.w2)
  • "Use of conventional needles and syringes is impractical and hazardous for large numbers of lambs under field conditions." [1998](J35.155.w1)
  • While use of a bloodless castration clamp (e.g. Burdizzo) across the whole scrotum or tail immediately after rubber ring application may reduce acute pain following rubber ring castration, use of conventional clamps may be difficult for one person working alone. Additionally, incorrect use may cause inappropriate tissue damage, and use of a clamp causes a brief bout of intense pain at the time of application. [1997](J35.155.w1)
  • For maximum effect of local anaesthetic, a period of at least two minutes between injection of the local anaesthetic and application of the castration and tail docking would be required; this may be considered too long for practical on-farm use. [1999](J24.77.w1)
  • Use of either local anaesthetic delivered by a needleless injector, or a bloodless castrator applied in addition to with rubber ring castration and tail docking is unlikely to be widely accepted due to increased costs associated with increased time taken for the procedure for each lamb as well as, in the case of the local anaesthetic, the cost of the applicator and the local anaesthetic. These costs are not considered justified because of the poor economic returns from fat lambs. Economics apart, the needleless injector was considered more acceptable and easier to use than the bloodless castrator. [2004] (J3.154.w2)
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Authors & Referees

Authors Dr Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee Suzanne I Boardman BVMS MRCVS (V.w6)

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