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Eggs of the 15 species of cranes. Click here for full-page view with caption. Eggs in an incubator tray. Click here for full-page view with caption. Crane on nest with egg. Click here for full-page view with caption. Grus rubicunda - Brolga with chick and egg on nest. Click here for full-page view with caption. Switching eggs for incubation. Click here for full-page view with caption. Whooping cranes on nest with egg. Click here for full-page view with caption.  Monitoring and recording egg weight during incubation. Click here for full-page view with caption. Fertile egg, five days. Click here for full-page view with caption. Infertile egg, seven days. Click here for full-page view with caption. Candling an egg. Click here for full-page view with caption. Weighing an egg. Click here for full-page view with caption. labelling an egg. Click here for full-page view with caption. Buddy egg monitor. Click here for full-page view with caption. Egg hatching. Click here for full-page view with caption. Crane chick hatching. Click here for full-page view with caption. Crane chick hatching. Click here for full-page view with caption. Crane chick hatching. Click here for full-page view with caption. Crane chick hatching. Click here for full-page view with caption. Crane chick just hatched. Click here for full-page view with caption. Newly-hatched crane chick being examined. Click here for full-page view with caption. Wattled crane hatching - Click here for full-page view with caption.

Introduction and General Information

  • Correct incubation conditions are important for development and hatching of eggs. The required conditions vary considerably between species, and some species appear more exacting in their requirements than others. Minor deviations in correct temperature may lead to a slightly shortened or lengthened incubation period, while greater variation may cause failure to develop or hatch, or result in weak chicks. Incorrect incubation conditions have also been implicated in some developmental problems of neonatal birds.
  • In general, correct incubation conditions are most crucial early in incubation, with small variations being tolerated better by the embryo later in development. For this reason, eggs are sometimes left with the parents initially for seven to ten days until they have been "set" and transferred to an artificial incubator after this most crucial period, in the hope that the birds will then lay again. Alternatively, eggs are placed under a broody initially, before being placed in an artificial incubator. Both procedures may improve hatching success compared to complete artificial incubation.
  • Egg cleanliness is of vital importance; it has been shown that poor hygiene and dirty eggs may significantly reduce the percentage of eggs hatching successfully. It is important that the laying sites are clean as well as conditions following egg collection. Eggs cool down once laid, therefore the contents shrink and air is drawn into the egg: bacteria may be drawn in at the same time. Invasion of bacteria such as Staphylococcus spp., Salmonella spp. and Escherichia coli may lead to death of embryos or neonates. Eggs may be cleaner if they are collected immediately after laying rather than after they have been "set".
  • Eggs which are deformed should not be incubated.

Management of damaged eggs

  • Eggs which are noted to be cracked at the time of collection are generally discarded, and grossly contaminated eggs may also be discarded at this time. If such eggs are particularly valuable, they should be separated from other eggs for incubation, due to the greater risk of infection.
  • Eggs which become cracked during incubation may be repaired, if the crack is small, with e.g. surgical grade cyanoacrylate glue, candle wax dripped onto the crack, nail varnish, correction fluid or sticky tape (it has been suggested that products containing acetone should be avoided, due to possible toxicity (B12.5.w10). Eggs which are cracked should be incubated in an incubator (not under parents or broody), with extra care taken in their handling and monitoring. It is important to ensure that the material used to cover the crack is applied to the minimum surface of the shell required to seal the crack. A thin layer of bone cement may be applied over a crushed area of shell and a hole in the shell may be repaired by gluing an appropriate piece if sterilized shell, parafilm, tissue or gauze over the defect. Care should be taken to avoid sealing over larger areas of the shell than absolutely necessary as this prevents necessary gaseous exchange.
  • If the shell membranes have been penetrated the egg is likely to have become contaminated with pathogens and the yolk, embryo or blood vessels may have been physically damaged. Hatchability is greatly reduced.
  • A pipped egg which is being parent or broody incubated and becomes damaged should be moved to a hatching incubator.
  • Eggs which fail to hatch normally may require assistance.

(J3.103.w1, B12.5.w10, B29, B37.x.w1, B41, B108, B115.4.w1, B119.w1, B139, P3.1987.w1).

Minimising bacterial contamination

  • Bacterial infection may occur transovarian, or following oviposition, particularly as the newly-laid egg cools when bacteria on the shell may enter the egg due to the temperature differential. Bacterial contamination following egg laying can be minimised by removal of gross contamination and by fumigation before incubation. (P1.1989.w5)
  • Injection of gentamicin into the albumin appears to be successful for treatment of bacterial infection inside the egg. (P1.1989.w5)
    • Experimentally, injection of 0.2 mg gentamicin in a volume of 0.1 mL into chicken eggs (each 51-58 g) on day 15 of incubation did not adversely affect incubation of normal (non-infected eggs). Injection into eggs which showed candling evidence of abnormalities (degeneration of the embryo vascular supply) following experimental or natural infection allowed a significantly greater number of eggs to hatch (4/6, compared with 2/49 untreated experimentally infected eggs; Chi Square test p < 0.001). For three naturally infected eggs, one of which was treated, the treated egg hatched while the others failed. (P1.1989.w5)

Records

  • Accurate and detailed records are very important in incubation. All eggs should be individually identified and details recorded including the identity of the parents, and details of their pedigree, nutrition and breeding and incubation behaviour, initial weight, date of setting, details of incubation such as results of candling, incubator used, weight loss (if this is being monitored) expected and actual hatching dates, as well as evaluation of the hatched chick or results of investigation into eggs which fail to hatch.

(B42, B119.w1).

Waterfowl Consideration
  • In waterfowl, hatching success may be improved if the eggs are parent- or broody- sat for the first ten days of incubation (P3.1987.w1).
  • Note: incubation periods are given on the individual species pages linked from Waterfowl Species
Crane Consideration
  • In the wild, both cranes take turns sitting on the eggs, but often more than half of the incubation is carried out by the female, with the male standing guard. The female generally incubates at night. (B115.1.w10)
  • Natural incubation, broodies or incubators (artificial inclubation) can all be used. (D437)
  • Generally the best rates of hatching are produced by natural incubation or a combination of parent incubation and artificial incubation. (B115.4.w1)
  • The first 7-10 days are the most critical; parent or foster-crane incubation during this period is preferable. (B115.4.w1)

Incubation periods:

(B115.4.w1)

(See also information given on the individual species pages).

Determination of fertility

It is important to determine whether or not eggs are fertile. 

  • Consistent infertility may indicate management problems, physical or behavioural problems in the breeding cranes, disease, genetic problems such as inbreeding depression. (B115.4.w1)
  • Infertility must be distinguished from early embryonic death (EED); if EED is occuring, the reasons need to be determined and corrective measures instituted; (B115.4.w1)
  • Infertile eggs take up nest or incubator space which could be used for fertile eggs; (B115.4.w1)
  • If eggs are being parent incubated, recognistion of infertility allows early removal and possible re-laying by the parents. (B115.4.w1)
  • Methods include:

Transportation of eggs

Fresh eggs

  • No special requirements. protect against excessive cooling (freezing) and excessive heating. Protect from physical force. (B115.4.w1)

Short-distance travel of incubated eggs

  • For quick transfers taking less than five minutes (e.g. from parents to incubator), cushion the eggs against rough movement, and protect them from severe cold/rain/winds.

Long distance travel of incubated eggs

  • Specially constructed portable incubators are required. (B115.4.w1)
  • A portable incubator suitcase has been developed by Patuxent: (B115.4.w1)
    • A reinforced cardboard suitcase is lined with polyurothane foam for insulation.
    • Hot water bottles, filled with water at 51.7 C (125 F) are placed in the bottom of the suitcase. Polyurethane foam inserts are placed above the hot water bottles. These contain egg-shaped pockets (half in the base, half in the lid) interconnected by air channels which run between the pockets and to the edges of the foam inserts, to allow convection and equilibration of temperature through the incubator.
    • The eggs are placed inside, the suitcase is closed and a thermometer is inserted through a hole in the side or lid so it lies in an air pocket close to the eggs. This is monitored constantly and the temperature maintained between 34.4 - 37.2 C (94 - 99 F).
      • The lid is opened and the eggs fanned if the temperature rises too high. (B115.4.w1)
      • The lid is kept closed to retain heat. 
      • The hot water bottles are replenished when the temperature falls below 34.4 C (94 F) or every two hours. 
    • The suitcase is kept on a person's lap and may be lifted up above the lap to provide extra protection from sudden starts or stops, bumps and vibration, to prevent rupture of blood vessels or embryonic membranes.
    • It is particularly important to protect from physical forces eggs which are in the early stages of incubation. (B115.4.w1)
  • A wooden box has been developed by ICF for international shipments of 24 hours or longer. (B115.4.w1)
    • The egg compartment is separate from the compartment containing hot water bottles, so the eggs do not need to be disturbed when bottles are changed. (B115.4.w1)
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Parent Incubation

  • Parent incubation generally provides the ideal conditions of temperature and humidity for development and hatching. However, not all species or individuals are equally good sitters, particularly in captive situations, in which birds may be disturbed and not feel secure. Additionally, small species in particular are vulnerable to predation while sitting, especially if nesting in an open site. Also, normal incubation behaviour may not be suitable for birds being maintained in an environment very different from their native habitat.
  • If allowed to sit, hatch and rear their chicks, most birds will produce only one clutch a year, whereas two, three or even more clutches of eggs may be produced if the eggs are removed.
  • It may be less easy to monitor parent-sat eggs for fertility and continued development, with an attendant risk of disturbing the birds.
  • In captive conditions it may be more likely that nesting materials will not be fresh and clean, but contaminated with droppings, or include mouldy vegetation.

(B42, B106, V.w5)

Waterfowl Consideration
  • As with other birds, parent incubation should provide the optimum conditions for the developing embryos.
  • In mixed-species enclosures there may be competition for nest sites and also dumping of eggs by some birds into the nests of other birds. In general, a pair of waterfowl occupying their own pen are less likely to be disturbed by other birds and more likely to sit successfully.
  • Both predation (of eggs and of the sitting female) and disturbance may be major problems, particularly for birds that have chosen sites which cannot be described as ideal.
  • Swans and geese frequently are good at sitting their own eggs, and ducks may also sit tightly if not disturbed excessively. Swans and many geese are commonly left to sit their own eggs, and to rear the young. Their larger size, well-defined territories and continuing strong pair bond reduces the chance of losses from predation of eggs.
  • With species such as the Cape Barren goose (Cereopsis novaehollandiae - Cape Barren goose), which lay their eggs during the winter, consideration must be given to the practicalities of incubation in winter conditions and the additional stress placed on the birds, unless they are in sheltered winter accommodation.
  • Most species of waterfowl can be stimulated to lay a second clutch of eggs if the first clutch is removed. However, females commonly change their nesting site due to the "predation" of the eggs and may stop laying if eggs are removed from all nesting sites. It may be advantageous to allow birds to sit and hatch eggs of their own or another more common species after a second clutch has been laid.
  • Birds which are sitting may leave the nest for only a short time each day. In species in which only one parent incubates the bird may lose a considerable amount of weight over the period of incubation and it is important to ensure that food is freely available at whatever time the bird leaves the nest to feed.
  • Waterfowl species vary in their response to disturbance at the nest site. Some are quite tolerant but others will desert the nest if subject to any disturbance. This makes regular inspection of the eggs for fertility and development difficult.
  • N.B. in allowing waterfowl to sit, hatch and rear their own offspring consideration should be made as to the likelihood of predation of the downies, whether or not suitable food will be available or can be provided, and the ease or otherwise of catching the downies to pinion them, if this is required. Leaving non-native species full-winged in open enclosures may be detrimental to local species and may also be illegal.

(B30, B40, B41, B94, B97, B128, P3.1987.w1, V.w5)

Crane Consideration
  • Parent incubation provides the natural variations in nest temperature associated with environmental changes and change-over of incubation between the parents, as well as a temperature gradient between the top and bottom of the egg. (B115.4.w1)
  • Captive cranes show overall nest attentiveness very similar to that shown by wild cranes, although they may show more frequent nest exchanges. (P1.1980.w8)
  • With parent incubation, no special facilities are required for incubation, and there are no risks of failures of electricity or mechanical functions of the incubator. (B115.4.w1)
  • Natural incubation (and chick rearing) also may enhance pair bonds and promote future breeding. (B115.4.w1)
  • Hatchability of eggs is greater with parent incubation than with artificial incubation. (J54.14.w1, P87.3.w2)
  • Minimising disturbance is advisable to improve incubation success. (D437)
  • Eggs are separated from one another; infectious diseases are unlikely to spread between eggs in different nests. (REF****)
  • Note: A back-up incubation system is needed for eggs which are deserted, endangered by bad weather, cracked or thin-shelled. (B115.4.w1)

Disadvantages

  • Naturally incubated eggs may be at greater risk of contamination from faeces, nesting material, soil etc., and of disease transmission from parents. (B115.4.w1, J54.14.w1)
  • There is a risk that the egg(s) will be accidentally or deliberately broken by the cranes. (B115.4.w1)
  • There is a risk of predation. (B115.4.w1)
    • This can be reduced by use of predator-proof fences and flight-netting of enclosures. (B115.4.w1)
  • There is a risk of nest abandonment by the cranes. (B115.4.w1)
    • This can be minimised by ensureing that incubating cranes feel secure in their territory and by avoiding disturbance. (D437)
  • It is less easy to monitor egg condition and embryo development. (B115.4.w1)
  • Incubating cranes stop laying, therefore production of cranes may be reduced; this is important if increased production is required e.g. for a reintroduction/reinforcement programme. (B115.4.w1)

Management of eggs during parental incubation

  • Observe each potential laying female two to four times daily, referring to a pre-marked form and noting appropriate observations. (B115.4.w1)

Initial care

  • If a new egg is spotted in the enclosure of unreliable parents, remove the egg immediately. If appropriate, replace it with a dummy egg to stimulate the cranes to incubate. (B115.4.w1)
  • Use clean gloves (latex or vinyl) when handling the eggs. (B115.4.w1)
  • Using a soft pencil (J23.21.w4) , mark the egg with an identification number, measure it (length and width) and weigh it. (B115.4.w1)
  • Consider disinfecting the egg by dipping in 10% povidone-iodine solution (e.g. Betadine) or a quaternary ammonium disinfectant or another non-toxic disinfectant. (B115.4.w1)
    • Patuxent disinfects all crane eggs; ICF does not. (B115.4.w1)
    • Disinfection is more important if the enclosures have been used for several years, so that a large burden of pathogens in the soil is more likely. (B115.4.w1)

During incubation

  • Observe the incubating cranes from a distance or using a blind, to determine their nest attendance. (B115.4.w1)
  • If the parents are often off the nest (poor nest attendance), particularly in cold weather, consider replacing the eggs with dummy eggs until the weather improves, meanwhile incubating the real eggs in a more reliable manner. (B115.4.w1)
  • At 5-7 days after laying, candle the eggs to find out if they are fertile. (B115.4.w1)
    • Eggs can be removed if they are infertile, or if they are fertile but re-laying is preferred. (B115.4.w1)
  • Monitor weight loss during incubation. (B115.4.w1)
  • At about 20 days, confirm development/viability by candling or flotation. (B115.4.w1)
    • Flotation can be used instead of candling at this stage (Patuxent) or if candling is unsuccessful, or it is suspected that the embryo has died. (B115.4.w1)
    • Remove any definitely infertile or nonviable eggs; these should be opened and subjected to bacterial culture and egg necropsy. (B115.4.w1)
  • If nonviable or infertile eggs are removed but continued incubation by the cranes is wanted, replace the eggs with viable eggs or artificial eggs. (B115.4.w1)

During hatching

  • Monitor more frequently from about two days before the expected hatching date. (B115.4.w1)
    • If parents become too agitated, reduce monitoring. (B115.4.w1)
  • At 1-2 days before hatching the chick's activity increases, it punctures the air cell and becomes vocal. Incubating parents purr frequently, communicating with the chick, and tend to hock-sit on the nest rather than lying on it, much of the time. (B115.4.w1)
  • When the chick pips, which is usually audible as its cheeping becomes louder, check that the pip is in the correct position, at the large end of the egg. (B115.4.w1)
  • Keep monitoring from 15-30 m using binoculars. (B115.4.w1)
  • If the chick has not hatched by 48 hours after pipping, close inspection of the egg is required; problem eggs usually will need to be taken from the parents to an artificial hatching facility for care. (B115.4.w1)
    • Failure to hatch at this stage may be due to drying of the membranes, which then adhere to the chick and prevent it from progressing, or to deformity of the chick. (B115.4.w1)
  • If a pipped egg becomes damaged and the chick is still alive, move it to a hatcher.
    • If it has probably been contaminated with faeces, soil etc., there is a risk of pathogens entering the yolk sac or ruptured blood vessels, or of their being aspirated by the chick. To counteract this there are two options:
      • 1) fumigate the egg. This may cause irritation to the chick, but this risk is outweighed by the need to prevent infection; OR
      • 2) give prophylactic antibiotic treatment to the chick while still in the egg of once it has hatched. (B115.4.w1)
  • As soon as possible after the chick has hatched, check that the yolk sac has been completely internalised. If it has, and the umbilicus is closed, apply iodine solution to the umbilicus as a preventative measure against infection. (B115.4.w1)
  • Weigh the chick; this gives a reference point for calculations of growth. (B115.4.w1)
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Broody / Foster Incubation

  • Broody hens are commonly used in aviculture and have been described, if properly managed, as "still the finest incubator yet developed" (B106). They have the advantage of being relatively simple to manage. In order to be sure that broodies will be available when required, a flock of appropriate hens must be kept, with attendant costs. The possibility of the hens carrying and transmitting disease must always be considered.
  • Silkies crossed with game hens are often considered to make ideal broodies.
  • Ideally, a broody should be given a clutch of eggs all of the same species and stage of incubation to sit.
  • Broodies may not be suitable for very small or very large eggs. Eggs with an abnormally thin or abnormally thick shell, in which maintaining correct weight loss is difficult and requires considerable manipulation of humidity, are not suitable for broody incubation.
  • Eggs which have been cracked or otherwise damaged should not be left under a broody for incubation.
  • Additional manual turning may be required with very large eggs.
  • Some broodies may not turn a coloured eggs mixed with white eggs.

(B37.x.w1, B106, B139)

Waterfowl Consideration
  • Broody hens may be used for incubating most waterfowl eggs. Obviously, carefully-selected reliable broodies should be used. Silkie-cross bantams are often considered excellent broodies, although larger hens may be required for larger eggs such as goose eggs (and small broodies should be used for small eggs). Good broodies are less easy to find now than previously, and a flock should be kept so that birds will be available at the correct time. A good steady broody is "worth her weight in gold".
  • Each broody should be provided with her own broody box. The box should be just large enough to contain the broody on her nest, and should be dark when the door is closed. This may be placed directly on the ground outside (with wire netting underneath to keep vermin such as mice and rats out), or under cover in a shed or barn. If outside, the boxes should be placed under a tree on in a similar shaded position. The bottom of the box should contain a thick turf turned grass-side down and with a hollow prepared in the middle for the eggs, and soft bedding over this. The turf should be thoroughly dampened prior to the start of incubation, and assists in conserving moisture. It is essential that sufficient bedding is available or the hen may scrape right down to the bottom of the box, with an associated risk of eggs becoming broken. Humidity may be increased during the incubation period by spraying eggs with water (e.g. with a plant mister) and damping turf while the broody is off the eggs. The amount of water required will vary depending on the weather and the siting of the nest boxes, with boxes directly on the ground requiring less dampening, except in very dry conditions.
  • Additional hand turning of eggs may be advantageous, particularly with very large eggs which may be less likely to be turned sufficiently by the broody.
  • The broody should be dusted with louse powder prior to incubation and put down on several dummy eggs initially to confirm that she is sitting tight. Hens are best introduced at dusk, as they appear to settle best at this time. Once daily the front of the brooder box should be opened and the hen allowed off the eggs, or lifted off gently if necessary (with care that eggs are not lifted up under the wings), for a short time to eat, drink, defecate and dustbathe. Good broodies will usually return to their eggs after a short time, or they may be encouraged to return. They should be off no more than five to ten minutes initially, although up to half an hour may be acceptable late in incubation if the weather is warm. Care must be taken if a broody must be placed back on her eggs that she does not damage eggs, for example by "pedaling" with her feet
  • Each broody box may lead out into its own small run, or several boxes may be placed in a yard or barn. Broodies will usually go back to their own box; it has sometimes been suggested that each should be tied by the leg to their box, although birds may be irritated by this and not sit properly.
  • Records should be kept indicating for each broody box indicating which hen is sitting, when she began sitting, when the present set of eggs was introduced and when they are due to hatch or to be moved, for example into an incubator.
  • The amount of moisture required may vary depending on the eggs. Eggs which would normally be laid and sat on in a damp marshy situation may require a higher humidity than eggs which are normally sat on in a dry tree hole.
  • Best results are obtained if the eggs under any one broody are all of the same species and stage of incubation: a whole clutch should be set under the broody together.. Results may be much poorer if a mixture of eggs of varying ages and mixed parentage are placed under the broody.
  • Ducks, for example mallard (Anas platyrhynchos - Mallard), may also be used to sit difficult eggs, e.g. Hooded merganser - (Lophodytes cucullatus - Hooded merganser). Mallard ducks, once sitting, make very reliable broodies. Domestic waterfowl may also be used, particularly Call ducks, and ringed teal (Callonetta leucophrys - Ringed teal) may be used for example to sit eggs from Smew (Mergellus albellus - Smew) or Bufflehead (Bucephala albeola - Bufflehead), which lay very similar eggs (B29, B41).

(B7, B29, B40, B41, B95, B97, B106, B108, B139).

Crane Consideration Foster cranes
  • Foster cranes can be used to incubate crane eggs. (B115.4.w1, J54.14.w1, P1.1980.w8)
    • Foster cranes need to have their own eggs, at the same stage of incubation as the egg(s) they are to foster. If the foster pair breed at about the same time as the donor species, this is not difficult to arrange, although several pairs of foster cranes should be available to ensure one will be in the correct breeding condition to incubate the eggs. (B115.4.w1)
    • If necessary, the breeding cycle of one or both species (foster and donor) will need to be manipulated, by using lights to change the photoperiod, or by removing eggs from the fosters to promote re-laying. (B115.4.w1)
    • Note: costs and labour requirements to maintain foster pairs of cranes to incubate eggs from endangered crane species are higher than if artificial incubators are used. (J54.14.w1)
  • Wait until a potential foster pair is sitting well on their own eggs before swapping these for the valuable foster eggs. (P1.1980.w8)
  • A single pair of foster cranes, sitting well, can if necessary (if not many foster pairs are available) incubate up to three sets of eggs in a given season, for the crucial period of incubation: the first 7-10 days. (B115.4.w1)
  • If eggs from a pair of cranes are moved and incubated by foster parents, the parents may lay again in the same season, increasing the rate of propagation. (J54.14.w1)
  • In general, this method has the same advantages and disadvantages as for parent incubation. (B115.4.w1)

Broody hens

  • Broody hens can be used to incubate crane eggs. (B115.4.w1, D437)
  • A single egg can be set under each broody. (B115.4.w1)
  • Large broodies can sit on two crane eggs. (N28.10.w1)
  • Because the size of crane eggs makes it unlikely that broody hens can turn them effectively, it is important to turn each egg by hand (D437) at least four times a day. (B115.4.w1)
  • Large breeds such as Cochins, Brahmas or Langshans are needed for incubating crane eggs. Bantams [which often are good brooders) may be too small to cover the egg properly. (B115.4.w1)
  • Broodies may be used for the whole incubation period or just for the first, most important, ten days (before transferring the eggs to an artificial incubator). (B115.4.w1)
  • If a broody is used to incubate two crane eggs, they should be transferred to a hatcher at the point of chipping; if left with the hen for hatching there is a risk of her crushing the emerging chicks. Also, she is likely to want to lead them from the nest before they are ready. (N28.10.w1)
    • Crushing of the chick during hatching has been reported. (P108.9.w2)
  • Only hens which have gone broody and sat tightly for a few days should be given a crane egg to brood. Move the hen from the main flock to a broody box and initially give her dummy eggs to sit. If she continues sitting tight then give her a real egg. (B115.4.w1)
    • Line the bottom of the broody box with indoor-outdoor carpeting, and form a nest out of straw or grass before placing the hen into it. (B115.4.w1)
  • Once daily, each broody should be released from the broody box to eat, drink, defecate and exercise. Lift the broody off the egg carefully, by slipping one hand under her breast to lift and placing the other hand over her back, taking care that she dose not start kicking the egg(s). Close the broody box door while the hen is out. After her exercise period, gently lift the hen back up to the edge of the nest and let her step in and settle on the egg. (B115.4.w1)
  • A hen which starts defecating in the nest is no longer broody. A hen which is restless and eager to leave her nest is no longer broody. (B115.4.w1)
  • A hen which becomes too thin needs to be removed from brooding duties and placed in the laying flock or a separate pen to stop brooding. (B115.4.w1)
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Artificial Incubation

  • Artificial incubation is commonly used in aviculture. Eggs incubated in this way are safe from predation and are not at risk of being deserted by the bird sitting on them, for example due to disturbance. Eggs in incubators are at risk if the power supply to the incubator fails, for example if there is an electrical power cut.
  • Artificial incubation allows many more eggs to be incubated than parent incubation and with less effort than maintaining broodies. However, very precise control and attention to the progress of individual eggs is required for the best results.
  • Accurate control of temperature and humidity are vitally important in artificial incubation. Cleanliness is also very important; the ease with which an incubator may be cleaned and disinfected is an important consideration when choosing an incubator.
Incubation Facilities:
  • The area in which incubators are kept should be easily cleaned and well ventilated, and should also be maintained at a constant temperature.
  • Most modern incubators are electric, although paraffin and gas powered incubators do still exist. Incubators vary greatly in size, may be still air (in which air moves by convection) or forced air (in which air is moved using a fan) and may or may not include automatic egg turning.
  • All incubators also require added water to maintain the correct humidity. This is usually provided in the form of one or more water trays.
  • Still air incubators, which have a temperature gradient from the top (higher temperature) to the bottom of the incubator may approximate the natural conditions in a nest (in which the incubating parent is providing heat from above), but they may easily be overloaded and the eggs then poorly ventilated. Forced air incubators have a much more uniform temperature throughout, and better ventilation, and may be used for many more eggs.
  • N.B. Individual preference plays a large part in choosing an incubator. In general, better results are likely to be obtained if the operator is familiar with, and comfortable using, the incubator.
  • Incubators should be cleaned and disinfected (and fumigated if required - see: Formaldehyde Fumigation of Incubators) before the breeding season. A disinfectant suitable for incubators should be chosen and care is needed in cleaning the Once clean, they should be set up without any eggs and switched on.
  • After the incubator has warmed up and appears to be at the correct operating temperature, it may be tested by incubating some bantam eggs. The temperature should be monitored and recorded several times daily, but adjusted on the basis of average daily readings rather than by micro-correction every few hours.
  • Wet-bulb readings should also be monitored to indicate humidity levels. A pattern of a slight rise in readings on the wet-bulb thermometer may indicate a soiled wick and this should be changed (B42).
  • For ideal results, all the eggs inside one incubator should be of the same age (stage of incubation) and size. In practice, eggs of different sizes and ages are commonly incubated in the same machine.
  • Eggs close to the end of incubation produce a considerable amount of heat and therefore contribute locally to the air temperature, particularly in a still-air incubator.
  • Large late-incubation eggs should not be placed near to small, newly-set eggs as they may affect their incubation temperature.
Temperature:
  • Incubators are most reliable if kept in a room with a constant temperature. Maintaining a steady incubator temperature inside a room which varies widely in temperature is practically impossible.
  • The temperature inside an incubator should be measured with a thermometer. This may be either a traditional mercury thermometer or an electronic thermometer. The bulb of the thermometer may be placed inside a blob of Plasticine or similar to reduce changes in readings due to minor fluctuations and give an average reading. It is important to make sure that the readings on the thermometer are accurate or, if there is an error, that the error is known, stable and can be corrected for. New thermometers should be checked against one known to be accurate. Either traditional mercury thermometers or digital thermometers may be used.
  • Even in a forced air incubator there will be differences in temperature within an incubator, which may be mapped by placing thermometers in different places within the incubator. In a still air incubator the temperature varies vertically within the incubator and there may be a difference of several degrees between the bottom and the top of the incubator. The temperature should be kept at that required by the eggs at the level at which the eggs are kept. In order to monitor this, a thermometer should be placed at the same level as the eggs.
  • N.B. the temperature will fall when the door is opened to add, remove or manipulate eggs. These procedures should be carried out quickly but carefully.
  • For normal development, eggs must be maintained within a narrow temperature range. Both too high and too low temperatures may be deleterious to eggs, although in general eggs are more tolerant of low than high temperatures:
  • Incorrect temperatures affect incubation time, with earlier hatching if the temperature has been slightly high, later hatching if the temperature has been slightly low.
  • Temporary cooling (as may occur naturally when an incubating bird leaves the nest to eat etc.) does not appear to be deleterious.
  • Constantly slightly low temperatures may result in slow development and late hatching. If the temperature is maintained at a sufficiently low level, deaths may result.
  • A temperature which is too high by a few degrees may be lethal and even a rise of just 1.0-1.5 C (2-3 F) may cause embryo death after perhaps four or five days.
  • See: Early-Embryonic-Death, Mid-incubation Embryo Death, Dead-in-Shell, Hatching Problems, Congenital Abnormalities
Humidity:
  • Humidity levels can be measured with a wet-bulb thermometer.
  • A wet-bulb thermometer is an ordinary thermometer in which the bulb is kept damp by means of a "wick" of covering the bulb and dipped into a small container of water. Evaporation from the wick reduces the temperature of the thermometer bulb.
  • Since evaporation is greater in a drier environment, a lower temperature reading indicates a lower humidity and a higher temperature reading indicates a higher humidity. A dirty wick gives a falsely high reading. The distance from the thermometer to the water reservoir for the wick should be about one inch (2.5 cm).
  • Relative humidity is proportional to the wet bulb reading if the dry bulb reading is constant. Tables indicating relative humidity for different wet bulb readings at different dry bulb temperatures are available in some incubation texts (e.g. B42, B115.4.w1, B139).
  • All incubators contain some method of maintaining humidity. Humidity is usually manipulated by changing the surface area of water trays placed in the bottom of the incubator - a larger surface area will produce a higher humidity. For example, trays may have a sloping floor, in which case increasing the depth of water will increase the surface area. Alternatively, surface area may be increased by placing sponges into the water with part of their surface coming out of the water.
  • N.B. humidity will drop when the incubator is opened and, particularly in a still air incubator, may take some time to return to the previous level. Spraying the floor of the incubator lightly with water before closing the incubator door may be used to increase the rate at which humidity is restored.
Weight loss during incubation:
  • Eggs normally lose a total of 18% of their weight during incubation, due to loss of water vapour which diffuses across the egg shell (J55.76.w1). Eggs should lose 15% of their weight from the start of incubation to the start of hatching (internal pipping). Monitoring and if necessary manipulation of their weight loss may be used to improve hatching success.
  • For ideal results, each egg should be weighed individually on an accurate balance and the actual weight loss plotted on a graph and compared with the ideal weight loss for that egg. This may be done by hand or using an appropriate computer programme.
  • The correct rate of weight loss early in incubation appears particularly important for hatchability; incorrect early rates of weight loss may be fatal to the embryo despite later correction giving the required overall weight loss.
  • If weight loss is too fast or too slow, it may be manipulated. N.B. Correcting the rate of weight loss after the first third of incubation is much more difficult.
  • If several incubators are kept at slightly different relative humidities, an egg may be moved into an incubator at higher humidity if it is losing weight too fast, or lower humidity if it is not losing weight sufficiently fast. Other methods involve altering the porosity of the egg shell.
  • N.B. in general, eggs which are normally incubated in very damp conditions are likely to require a higher level of humidity during incubation than eggs which would be incubated in the wild in very dry conditions.
Excessive weight loss and its correction
  • Weight loss may be too fast due to thin shells or low incubator humidity. 
  • Weight loss may be decreased by increasing the incubator humidity. 
  • Part of the eggshell may be painted over with nail varnish to decrease water loss through the shell. 
  • In extreme cases of excessive weight loss, rehydration may be used. This involves completely submerging the egg in cold (approximately 10C, 50F) sterile water for up to five minutes (shorter times are preferable) daily or even more frequently, with accurate weighing to monitor the uptake of water during the procedure. The cold temperature causes the egg contents to contract, drawing water into the egg. The frequency and duration of dipping should be varied according to the degree of weight loss and the stage of incubation. Care must be taken not to over stress the embryo by dipping for too long. Dipping in antibiotic solution has been described for the first dip (3 mg tylosine tartrate (Tylan Soluble, Elanco Animal Health) in 1 litre sterile 0.9% saline giving 3000 parts per million tylosin solution). (B42, B115.4.w1, J54.2.w1, N1.92.w1).

Insufficient weight loss and its correction

  • Weight loss may be too slow due to thick shells or high incubator humidity.
  • Weight loss may be increased by decreasing the incubator humidity.
  • Porosity (and therefore water loss) may be increased by careful thinning of the eggshell using sandpaper.
Incorrect humidity and egg weight loss may lead to loss of embryos or chicks at several stages of incubation and hatching. See: Early-Embryonic-Death, Mid-incubation Embryo Death, Dead-in-Shell, Hatching Problems
Turning:
  • Either automatic or hand turning may be used.
  • If eggs are turned by hand they should be turned several times per day (minimum five times daily), and always turned an odd number of times so that the egg is on opposite sides for the longest internal (overnight) on alternate nights.
  • Eggs should be marked with "O" on one side and "X" on the opposite side, and all turned so that the "O" is uppermost on all the eggs after one turning and the "X" is uppermost after the following turning.
  • Eggs should be turned in one direction one day and the other direction the following day (i.e. rotated along their long axis clockwise and anticlockwise alternately). Continual rotation in the same direction may lead to problems such as twisting of the chalazae, rupture of the yolk sac or rupture of blood vessels in the embryo.
  • Various means of automatic turning may be used. Eggs may be laid on their sides on rollers which move one way then the other alternately, or on a flat tray with movement provided by the movement of rods one way then the other (or the rods may stay still while the tray moves). An alternate method involves eggs being placed small end downwards in trays which are tilted to 45 degrees one way then 45 degrees the other way.
  • N.B. if automatic turning is used, monitoring is required at different times of day to confirm that the eggs are being turned.
  • See: Early-Embryonic-Death, Mid-incubation Embryo Death, Dead-in-Shell, Hatching Problems
Ventilation:
  • Developing embryos require a flow of air to provide oxygen for respiration and to remove carbon dioxide.
  • Rigid egg trays with an open mesh construction should be used to allow air to flow around the eggs and the addition of extra obstructions to air flow should be avoided.
  • N.B. Air flow is lower in still air than in forced-air incubators and it is important not to overcrowd the eggs.
  • The movement of air in an incubator containing eggs will be different from in the same incubator when empty, which is one reason why the incubator function should be checked with bantam eggs.
  • Temperatures within the incubator may fluctuate if air flow is obstructed. If this cannot be rectified it is important to place eggs only in the most stable temperature areas of the incubator.
  • See: Early-Embryonic-Death, Mid-incubation Embryo Death, Dead-in-Shell, Hatching Problems
Monitoring development:
  • The development of the embryo within the egg is monitored most commonly by means of candling - shining a bright light through the egg (see: Candling). Candling is difficult if eggs have a very thick or patterned shell.
  • Eggs may also be tested by Egg Floatation. The egg is placed in a bowl or bucket of water. Fresh eggs will sink, late-incubation eggs will float and live eggs close to incubation can be seen to move.
Records:
  • Accurate and detailed records are very important in incubation.
  • In addition to records of individual eggs (see above: Introduction and General Information) it is important to keep records of the temperature (dry bulb) and the humidity (from wet bulb) of each incubator, so that increases or decreases in temperature or humidity are detected early and can be corrected.
  • Trends in temperature and humidity may be most easily seen if plotted on a graph.
  • Temperature and humidity should be recorded at least two or three times per day.
  • Automatic turners should be checked at different times of the day to confirm that they are actually operating and turning the eggs.

(J23.29.w1, B12.5.w10, B37.x.w1, B42, B106, B115.4.w1, B119.w1, B139, V.w5)

Waterfowl Consideration
  • Waterfowl eggs vary considerably in size (e.g. 25 grams for a teal egg, versus around 300g for a swan egg) and in the normal environmental and climatic conditions under which they would be incubated. Correctly controlling incubator conditions (temperature and humidity) for all the different eggs may be challenging (N1.89.w1)
  • Hatching success may be improved by using parent or broody incubation for the first ten days. Conditions in the early stages of incubation are more critical than late in incubation.
  • For waterfowl eggs, incubated at 99.5F dry bulb temperature, with a wet bulb reading of 84F, giving 55% relative humidity is suggested as a starting level (B42).
  • Incubation conditions for waterfowl eggs of 37.2C (99.0F) dry bulb temperature and 31.1C (88F) wet bulb temperature, with a hatcher at 36.9C (98.4F) dry bulb, 31.1-32.2C (88-90F) wet bulb have been suggested (J23.29.w1).
  • For further information on problems see: Early-Embryonic-Death, Mid-incubation Embryo Death, Dead-in-Shell, Hatching Problems, Congenital Abnormalities

(P3.1987.w1, V.w5)

Crane Consideration Advantages
  • Removes the risk of egg breakage or abandonment by incubating cranes. (B115.4.w1)
    • It is very useful for ensuring proper incubation of eggs of inexperienced or unreliable cranes. (P76.1989.w1)
  • Safe from predation. (B115.4.w1)
  • Keeps the egg clean and free of faeces, soil etc. (B115.4.w1)
  • Removes the risk of disease transmission from the parents to the egg or newly-hatched chick. (B115.4.w1)
  • The egg can be monitored closely, e.g. for correct weight loss and embryo development. (B115.4.w1)
  • This method is essential for damaged (cracked) eggs or those with thin shells. (B115.4.w1)
  • This allows incubation following injury or death of the parents. (P76.1989.w1)
  • This allows multiple clutching. (P76.1989.w1)

Disadvantages

  • There is a risk of losing many eggs if an incubator fails.
  • Incubators do not provide the same temperature gradient from top to bottom of the egg that is produced by a bird sitting on the eggs, nor the same turning, nor the temperature variations seen at change-over time of incubation, not the fluctuation associated with ambient temperature changes. (J54.14.w1, P76.1989.w1)
    • Biotelemetric monitoring of an artificial egg in the nest of a pair of white-naped cranes showed that: (P76.1989.w1)
      • eggs are turned approximately every hour, but when they are turned they are turned several time over a period of up to ten minutes. (P76.1989.w1)
      • The mean maximum egg temperature was 38.0 C. (P76.1989.w1)
      • There was a considerable vertical thermal gradient - from 13.8 C on day one of incubation to 5.9 degress on day 29; overall, the thermal gradient around the egg decreased during incubation. However, the significance of the temperature gradient in terms of embryo development is unknown. (P76.1989.w1)
      • Nest humidity varied considerably depending on ambient air humidity. (P76.1989.w1)
      • Video recordings showed that the female was on the nest 66.5% of the time, incubating for a mean of 69.2 minutes (for 32 incubation bouts) while the male was on the nest 26.7% of the time, incubating for a mean of 32.2 minutes (for 38 incubation bouts. Neither bird was incubating for 6.9% of the time; on average, the time off the nest between incubation bouts was only 3.9 minutes (range 1.2 - 9.5 minutes). (P76.1989.w1)
  • Note: Results may be improved if the eggs are incubated by cranes initially (e.g. for the first two weeks). (B521.19.2.w19b)

Egg handling and initial care

  • Always handle the eggs using clean or sterile latex, plastic or vinyl gloves. (B115.4.w1, J54.2.w1, P90.1.w2)
  • Wipe off any faeces or dirt using a soft cloth. (B115.4.w1)
    • Stubborn, dried-on materials can be removed with fine sandpaper, but great care must be taken not to damage the surface of the egg. (B115.4.w1)
  • Weigh the egg and measure it (length and diameter). (P90.1.w2)
  • Write an identifying number on the small end of the egg in pencil. (J23.21.w4, P90.1.w2)
  • Before putting the egg in the incubator, fumigate the eggs (see Formaldehyde Fumigation of Incubators). NOTE: only fresh eggs (not incubated at all) or eggs which have been incubated for at least five days can be fumigated.
  • OR as an alternative to fumigation, particularly for eggs which may have been incubated for up to five days, or for an unknown time, dip the egg in 10% povidone-iodine solution at 43.3 C / 110 F, then allow the egg to dry at room temperature before placing it in the incubator. (B115.4.w1)
    • Eggs can be dipped in a 20% quaternary ammonium solution or 1% betadine solution. (P90.1.w2)
  • Eggs can be stored for up to 10 days before incubation is started. (J23.14.w5)
    • Store in cool conditions (12.8 C), horizontally, and turn 180 degrees daily. (J23.14.w5)
    • Allow cool eggs to warm to room temperature before placing them in the incubator. (J23.14.w5)
Incubation conditions

The correct incubation conditions are extremely important.

  • An alarm should be installed, set to sound if there is a power outage or the incubation temperature moves outside set parameters: above 38.3 C (101 F) or below 35.6 C (96 F). As well as an audible alarm in/near the incubation room, an alarm with an autodialler should be installed which will alert personnel even away from the incubator room. A flashing light may be used as an additional signal. (B115.4.w1)

Temperature and temperature control

  • The correct temperature (dry-bulb temperature) for crane eggs is 37.6 C (99.5 - 99.75 F). (B115.4.w1, P96.1.w1)
    • Temperature should be 36.5 - 38 C. (P91.1.w6)
    • 37.6 C (99.5 F) suggested. (B521.19.2.w19b)
  • Regular cooling of eggs, as occurs during natural incubation e.g. at nest exchanges, does not appear to improve hatchability of crane eggs, therefore maintenance in the incubator, in stable conditions, except while candling etc., is recommended. (B115.4.w1, P96.1.w1)
  • For each incubator there should be a main controlling thermostat plus a backup thermostat which takes over control if the main thermostat fails. (B115.4.w1)
  • Note: 
    • a rise in temperature of just 1.0-1,5 C (2-3 F) may be fatal, not necessarily immediately but after 4-5 days. (B115.4.w1)
    • a small drop in temperature below recommended is unlikely to increase mortality but may slow the development of embryos, delaying hatching. (B115.4.w1)
  • Each incubator should contain a dry-bulb thermometer which can be read from outside the incubator. (B115.4.w1)
  • Each year, thermometers accurate to 0.1 C (0.2 F) should be positioned in various places round the incubator to map the temperature variation within the incubator. (B115.4.w1)
  • Readings should be taken regularly several times a day and recorded. (B115.4.w1)
  • Note: opening the incubator causes the temperature to drop. When eggs need to be added or removed, carry this out carefully but rapidly, to minimise the time for which the door is open. (B115.4.w1)
  • The stability of the temperature inside the incubator is dependant on stable ambient conditions within the incubator room. (B115.4.w1)

Humidity level and humidity control

  • The correct humidity varies between crane species: (B115.4.w1, J23.21.w4)
  • Note: if the local humidity is high, adjust to give a wet-bulb temperature 1 C (1-2 F) lower than those suggested. If your facility is at high altitude with a lower air pressure, adjust 1 C (1-2 F) upwards on the wet bulb temperature. (B115.4.w1)
  • Wet-bulb thermometers indicate humidity as follows: the bulb of the thermometer is covered by a cotton wick which reaches into a reservoir of distilled water (so remains wet). The bulb of the thermometer is cooled by water evaporating from the wick. As the relative humidity increases, less water evaporates from the wick so the wet bulb temperature rises to closer to the dry bulb temperature. (B115.4.w1)
  • Humidity inside the incubator is controlled by evaporation of water from a reservoir, misting, and air flow through the incubator. Evaporation (and therefore humidity) can be increased by increasing the surface area of a water tray and/or by ensuring that the fan of the incubator blows air directly across the water tray. (B115.4.w1)
    • Distilled water can be used to prevent build up of minerals. (B115.4.w1)
    • Very large incubators may have a flow-through humidifying system which makes use of distilled water too costly. (B115.4.w1)
  • Note: opening the incubator causes the humidity to drop (as well as the temperature). It takes longer for the humidity to rise again after the door is closed than for the temperature to rise. Before closing the door, lightly spray the incubator floor with water to assist in raising the humidity more rapidly back to the usual level. (B115.4.w1)

Air flow

  • A constant flow of oxygenated air is needed to provide oxygen to the developing embryos in the eggs and remove carbon dioxide. Egg trays should have a rigid, open mesh construction to enable air to flow around the eggs.
  • To avoid disrupting the air flow, keep all trays in the incubator, and avoid adding obstructions. 
  • If air circulation is poor, there will be temperature variations within the incubator. 
  • If temperature variations continue to be a problem, eggs should be placed only where the temperature is most stable.
  • Air flow is controlled by vents: more air flow (and therefore lower humidity) when the vents are open, less (and therefore higher humidity) when they are closed. Note: it is important to keep the vents partially open at all times except during fumigation, to ensure sufficient air flow to the embryos. (B115.4.w1)

Egg position and turning

  • For automatically-turning incubators, make sure the eggs are placed in the trays securely so they cannot move freely and break or crack. 
  • Usually, set crane eggs horizontally so the big and small ends are at the same height. (B115.4.w1)
    • This position is used at ICF. At Patuxent, eggs are placed in the trays such that they are at a 20-30 degree lateral angle when the trays are flat, and as the trays tilt the large end is elevated 20-30 degrees when the tray tilts forwards and the small end is elevated 20-30 degrees when the tray tilts backwards. Occurrence of chick malpositions (which can be associated with egg positioning) is low at both facilities. (B115.4.w1)
  • The intervals between eggs being turned should be equal. (B115.4.w1)
  • If eggs are incubated horizontally it is important that successive turns should be carried out in alternate directions (i.e. clockwise then counterclockwise along the long axis of the egg) to make sure that the chalazae (the albuminous cords attaching the yolk to the shell membrane) do not get supercoiled. (B115.4.w1)
  • If eggs are to be hand turned (i.e. if automatic turning is not available) mark each egg with "X" on one side, "O" on the other to show easily whether, and to what extent, an egg has been turned. (B115.4.w1)
  • Eggs should be turned at least eight times daily. (B115.4.w1)
    • If an egg is not turned, the embryo may adhere to the shell membrane. (B115.4.w1)

Incubator hygiene

  • The warm, humid conditions within an incubator are ideal for growth of many pathogens. A clean, pathogen-free environment is required. (B115.4.w1)

Initial cleaning

  • Before the onset of the laying season, thoroughly clean all surfaces inside the incubator using a bactericidal and fungicidal disinfectant. To clean the wiring, use compressed air or a light spray of disinfectant. 
  • Once clean, allow the incubator to dry, then turn it on and raise the inside temperature to 26-37 C (80-100 F and relative humidity to 50-60 %.
  • If possible, fumigate the incubator, once it has reached working conditions, using formaldehyde. See: Formaldehyde Fumigation of Incubators
    • If fumigation cannot be carried out (e.g. for health and safety reasons), use an appropriate egg safe commercial disinfectant.

During the laying season

  • Incubators should be fumigated every two weeks, or weekly if eggs are being added frequently (every few days). See: Formaldehyde Fumigation of Incubators
    • Eggs which have been incubated for less than five days, or of unknown stage of incubation need to be moved to another incubator during fumigation.
    • Fresh (unincubated) eggs and eggs which have been incubated for more than five days can be left in the incubator during fumigation, to kill any pathogens on the shell.
  • Incubator water trays need to be cleaned and disinfected regularly.
  • If fumigation cannot be used, use a commercial spray disinfectant suitable for incubators and safe for eggs.

Monitoring (candling, weight loss, flotation) & Record keeping

Eggs
  • Eggs should be monitored by regular candling and, when appropriate, floatation. (B115.4.w1)
  • For very valuable eggs, weigh twice weekly. (B115.4.w1)
  • Keep a record of weights and a graph showing weight loss. (B115.4.w1)
  • Ideally, the egg should lose 15% (13-17%) of its original weight by the time of hatching. (B115.4.w1, B521.19.2.w19b, P96.1.w1)
  • Eggs which lose more or less than this amount may still hatch, either with or without assistance.

Incubator

  • The temperature and humidity inside each incubator should be checked and recorded at least twice or three times per day.
  • If an automatic turning system is in use, this should be monitored to confirm that it is turning the eggs.
  • Note: records not only allow early detection of trends such as temperature or humidityincreases or decreases, but also can be used to adjust incubator conditions if problems develop e.g. in hatching. 

(B115.4.w1)

Problems and problem solving

Cracked or damaged eggs

  • Damaged eggs need to be artificially incubated. (B115.4.w1)
  • Seal hairline cracks with surgical-grade cyanoacrylate or with candle wax (drip wax from a burning candle onto the shell). Ensure that the sealer is only applied along the crack(s) as excessive sealing can interfere with gas exchange and asphyxiate the embryo. (B115.4.w1)
  • Larger cracks and crushed areas also can be sealed using candlewax applied in the same manner (by dripping). (B115.4.w1)
  • Alternatively, for large crushed areas, apply a thin layer of bone cement over the affected area. (B115.4.w1)
  • To repair a hole, glue a piece of sterilised eggshell over the hole, or layer parafilm, gauze or tissue over the hole with glue.
  • Always apply repairing materials to the smallest possible area to avoid restricting gaseous exchange. (B115.4.w1)
  • Sealing too much of the shell also can cause the embryo to orient away from the sealed area, which may lead to malposition. (B115.4.w1)
  • Note: if the shell membranes have been damaged, it is likely that pathogens may have been introduced, or the yolk, embryo or blood vessels may have been physically damaged. (B115.4.w1)

Contaminated eggs

  • In general, once pathogens enter the egg, little can be done. However, sometimes infection of a contaminated egg can be prevented by dipping the egg in disinfectant, or by injecting the egg with antibiotics. (B115.4.w1)
  • Eggs which show signs of infection (odor, discolouration of egg contents) or are known to contain a dead embryo should be removed from the incubator immediately to avoid other eggs becoming contaminated. (B115.4.w1)
    • Note: eggs can explode due to pressure of gasses formed during decomposition; this scatters the eggs contents all over the incubator, contaminating the incubator and the other eggs. (B115.4.w1)
  • Eggs which are obviously contaminated, and at least some of those containing dead embryos or which are presumed infertile, should be cultured to detect microbial infections.
  • The origin of infection must be investigated if an infection is found. If there is a persistent problem of microbial contamination of eggs, swabs must be taken and cultured from the incubator, egg handling equipment and the birds (by cloacal swabs).
  • The incidence of infection can be minimised by good hygiene (see above): using sterile surgical gloves to handle eggs, plus scrupulous disinfection of all surfaces the eggs contact. (B115.4.w1)

Excess weight loss

  • This may be due to low humidity, high incubation temperature or an eggshell which is too porous or abnormally thin. (B115.4.w1)
  • See above (general information on Artificial Incubation) for further information.

Insufficient weight loss

  • This may be due to high humidity, low incubation temperature, a thicker than usual shell or one with blocked pores. (B115.4.w1)
  • See above (general information on Artificial Incubation) for further information.

Malpositioned or floating air cell

  • If the air space is floating or there are multiple bubbles, hatching is unlikely. The egg may be bacterially or fungally infected. (B115.4.w1)
  • If the air cell is stationary but displaced, the chick may die at hatching either because it orients correctly to the large end of the egg (but the air cell is not where it is needed for the chick to breath), so it drown or suffocates unless it quickly breaks through the outer shell) or it orients to the air cell and is otherwise malpositioned and cannot hatch. (B115.4.w1)
  • It may be possible to save such chicks by immediate assistance at hatching. (B115.4.w1)
  • If the egg is incubated large end upwards and turned by hand the chick may hatch successfully. (B115.4.w1)
Associated techniques linked from Wildpro

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Hatching

Hatching Facilities:
  • A higher humidity is required for hatching and a separate incubator should be maintained for this purpose. 
  • High humidity is very important to avoid the shell membranes drying out, sticking to the chick and being unable to turn properly and push its way out of the shell. 
    • Either a still air or a moving air incubator may be used as a hatcher. 
    • N.B. frequent opening of the incubator, by lowering humidity, may result in hatching problems. A hatcher with a clear top or panel is useful to allow monitoring of hatching without constant opening of the hatcher.
  • Hatchers tend to get dirty rapidly with bits of fluff, shell, etc. Debris from hatched chicks provides very good conditions for pathogens to grow. Frequent cleaning and sterilization is recommended, preferably after the hatching of each chick or batch of chicks. 
  • If chicks are hatching daily, two hatchers may be used, so that eggs may be in one hatcher while the other is being fumigated. If fumigation is not used, hatchers may be disinfected with a disinfectant of suitable efficacy and safety for use with eggs.
  • Chicks may be hatched inside individual plastic boxes within the hatcher. This will reduce contamination of the hatcher with fluff, bits of eggshell etc. and also allows easy monitoring of which chick has hatched from which egg.
  • See: Dead-in-Shell, Hatching Problems

****CHECK REFS

Hatching

  • Normal hatching occurs at the expected time time and without any help required (B42).
  • Stages of hatching:
    • Scratching and peeping phase. This first stage of hatching starts with internal pipping, when the chick breaks through into the air cell and starts to breath the air in the air cell. If the egg is held close scratching and peeping may be heard.
    • Pipping phase. This phase starts when the chick pips the shell - makes a small hole in the shell, in the middle of the upper edge of the air cell. This stage lasts until the chick starts to rotate.
    • Emergence starts when the chick begins rotating counterclockwise in the egg, breaking away pieces of shell along the edgd of the air cell, and lasts until the chick has freed itself from the shell.
    • Note: the duration of each phase of hatching is highly variable; if one phase is short, the next may be prolonged, and vice versa. 

    (P87.4.w1)

Hatching problems associated with incorrect incubation conditions:

  • Sticky, difficulty in final push after successful rotation, or difficulty in final rotation: low hatcher humidity, or low humidity during incubation (B42, B106).
  • Large/swollen chick: humidity too high during incubation (B42, B106).
  • Early hatch: slightly high incubator temperature. Chicks may be small and weak, may have an incompletely absorbed yolk sac, and may have minor malformations such as crooked toes. This problem also is associated with splay leg (B42, B106).
  • Late hatch: slightly low incubator temperature, temporary chilling during incubation, low hatcher humidity (B42). Low temperature is also associated with large, soft chicks and some malformations such as crooked legs or wry neck (B106).
  • Small weak chicks and large percentage dead in shell - low initial period humidity.
  • Large soft chicks, sticky with albumen, and unhatched pipped eggs requiring assistance - excess initial humidity.
  • Low hatcher humidity causes problems in hatching, pieces of shell stuck (B106).
  • Inadequate ventilation may produce soft swollen chicks gasping for air (B106).

(B42, B106).

Hatching assistance:

  • The chick's vigour must be assessed when deciding whether to intervene. (P87.4.w1)
  • Intervening too soon with a normal but slow chick may be harmful. (P87.4.w1)
  • It is very important to insure that the membranes are kept moist at all times. The hatcher humidity must be kept high, remembering that opening the hatcher to assist a chick inevitably decreases the humidity, and the membranes should be moistened with sterile saline.
  • Good hygiene during assistance is essential. Instruments used should be sterile. (P87.4.w1)
  • Assistance should take place in stages. Stopping after each stage of assistance gives the chick a chance to complete the hatching by itself, if the problem has been overcome, and reduces the chance of problems associated with premature hatching. (B41, B115.4.w1).
    • Assistance too early may lead to excessive blood loss as the external vessels are still functional and care must be taken not to remove a chick from the egg when it has not yet absorbed the yolk sac. 
    • If a hole is to be made in the membranes this must be made in an area free from active blood vessels. 

(B41, B115.4.w1).

  • If a chick has failed to break the inner membrane into the air space and appears to be weakening, it may be malpositioned.
    • A malposition may be visible on candling, with the tip of the bill visible near the air space, or the shell may be opened cautiously and the membrane moistened, which may reveal the position of the bill. (B115.4.w1)
    • Radiography may be used to show the position of the chick. (B115.4.w1)
  • If the bill is located away from the air space:
    • Remove a piece of shell from over the bill;
    • Make a small incision through the membrane (care not to cut active blood vessels - identify these and make the incision in a vessel-free area). 
    • Pull the bill through the shell sufficient far that the nares (nostrils) are exposed. 
    • Remove fluids from the airways if necessary. 
    • Put a loose cover of plastic or take over the area where the shell has been removed, keep the hatcher huidity high, and wait one to two days for yolk sac absorption and blood vessel contraction to occur.
    • Moisten the membranes as required to prevent them drying out.
    • Note that further assistance probably will be needed when the chick starts to hatch. Note: it is normal for there to be a period when the chick is quiet before it starts to hatch. Usually, if a tape recording of the adult crane's purring (brooding call) is played or imitated, the chick struggles and cheeps. If it remains quiet, and does not move, it may be too weak to hatch without assistance. [General not just for this situation???****]

    (B115.4.w1)

  • If pipping has occurred but hatching does not progress as expected, assistance may be required. 
    • Initially, remove the shell over the airspace. Using sterile water or saline, carefully moisten the membrane between the chick and the aircell so the chick and the blood vessels of the membranes are visible.
    • If the blood vessels are pale and empty, carefully peel back the membrane from around the bill, a little at a time, with pauses to allow the chick to emerge by its own efforts if possible. (B40, B108, B115.4.w1)
    • If necessary, blood vessels in the membranes can be tied off. (B115.4.w1)
    • Just lifting the head from under the wing and gently extending it may be sufficient to allow the chick to complete hatching (B41).
    • If the yolk sac has been absorbed and the blood vessels are contracted but the chick is weak, with oedema around the back of the head and neck, and it is failing to progress, further assistance may be required and it may be necessary to carefully pull the chick out of the egg. (B115.4.w1)
    • A weak chick can be treated immediately after hatching, or even before hatching is completed, by injecting it with fluids, glucose and steroids. (B115.4.w1)
  • N.B. Opinions differ as to whether and how much a chick should be assisted to hatch. A chick may be unable to hatch due to genetic problems resulting in malpositioning or general weakness, in which case assistance may promote the survival of birds with deleterious genes. However, hatching difficulties may also result from deficiencies in incubation - a man-made problem - with a chick which is genetically viable, or an abnormally thick shell which may be related to nutrition.

(B40, B41, B108, B115.4.w1, V.w5)

 

Waterfowl Consideration

(P3.1987.w1, V.w5)

Crane Consideration
  • The time at which the hatching process is expected to start can be estimated from the total time of incubation for the species minus the usual time taken for the hatching process to be completed. (P87.4.w1)
  • One to three days before the expected hatching date, candle the egg, mark the lowest point of the air cell (the point where it reaches closest to the small end of the egg) with a pencil mark and place the egg in the hatcher or in the bottom of the incubator with this spot uppermost: pipping should occur at this point. (B115.4.w1, P96.1.w1)
    • Hatching may be facilitated if the egg is placed with the pip point uppermost. (B115.4.w1)
    • It is easier to monitor progress if the pip point is uppermost. (B115.4.w1)
  • In the last two days before hatching, it is not necessary to turn the egg; it can be placed on the bottom of the incubator (assuming the incubator has automatically turning shelves), on a styrofoam pad with a central depression to hold the egg (B115.4.w1) or in a hatcher. (J23.21.w4)
    • Eggs in the hatcher should not be turned. (P90.1.w2)
  • Eggs can be sprayed with a mist of warm water during hatching to help prevent drying of the membranes. (P90.1.w2)
  • One hatcher should be used for each egg; if two or more eggs are expected to hatch at the same time, they can be placed in the same hatcher, with dividers to keep the chicks separate. (B115.4.w1)
    • Line the hatcher, or each hatcher compartment, with indoor-outdoor carpeting or similar to provide a non-slip surface for the newly hatched chick and protect its toes from the risk of getting caught in the wire floor. (B115.4.w1, J23.14.w5)
    • If more than one egg is in the hatcher, vinyl-covered wire can be used to divide it into separate compartments without blocking air flow. The dividers must be tall enough to stop the chicks moving from one compartment to another. (B115.4.w1)
  • The hatcher should be kept at 37.2 C (98.5 - 99.0 F) and as high a humidity as possible: to give a wet-bulb temperature of 32 C / 90 F or higher. (B115.4.w1)
    • Hatcher at 36 C. (P91.1.w6)
    • 37.2 C and 75% relative humidity. (B521.19.2.w19b)
  • Move eggs which are pipping to the hatcher: move the egg when it has pipped or when it has broken through into the air space (internal pipping); this can be detected because the chick will start vocalising (peeping). (B115.4.w1, P96.1.w1)
    • Move the egg to the hatcher two to three days before pipping. (P91.1.w6)
    • If a chick has broken into the air space and will be left unchecked overnight (or for several hours during the day), it is important to move it to the hatcher to avoid the risk of injury from it hatching in the incubator. (B115.4.w1)
  • The vigour of the chick can be estimated from the strength of the scratching and cheeping inside the egg. (B115.4.w1)
  • Monitor progress four times a day. Playing a tape recording of crane brooding calls, or imitating these calls, may stimulate movement and vocalisation. (B115.4.w1, B521.19.2.w19b)
  • Reductions in vigour of movements or cheeping may indicate weakening of the chick. (B115.4.w1)
  • Hatching should occur within 24-36 hours after the start of cheeping and scratching. (B115.4.w1)
  • Leave the chick in the hatcher for 24 hours before moving it to a brooder box. (P90.1.w2, P91.1.w6)
    • Leave the chick in the hatcher (quiet and dark) to rest after hatching until the excess fluid around the leg joints has absorbed before transferring it to a brooder box. This may reduce the development of leg problems. (N28.10.w1)
    • Give each chick a feather duster for security. (P90.1.w2)

Hatching problems

  • Hatching usually occurs within 14-36 hours from pipping. (P91.1.w6); within 24-36 hours (B521.19.2.w19b, P96.1.w1) Note: often there is a rest period of 12-24 hours between pipping and the continuation of hatching; it may take 36-48 hours from first pip to the completion of hatching. (J23.21.w4)
  • Eggs which fail to hatch within 48 hours after the first signs, or are becoming weaker (reduced cheeping or reduced movements), may need assistance. (B115.4.w1, J23.14.w5)
  • If assistance is given too early the yolk sac may not be resorbed properly, or may even be ruptured. (J23.14.w5)

Endoscopic diagnosis

  • Endoscopy can be used to assist diagnosis of hatching problems. (P4.1999.w1)
    • Mark the location of the aircell.
    • Using a burr type drill rotated between the thumb and forefinger, drill a small hole in the shell over the aircell.
    • Insert the endoscope into the aircell and examine the membranes.
    • Thickening or discoulouration may indicate infection; remove the endoscope and insert a suitably sized swam to take a culture sample.
    • If the membrane shows signs of dehydration, moisten the membrane with 0.1 - 0.5 mL sterile water, as required, so the membrane becomes somewhat translucent. 
    • Check the location and position of the embryo: the embryo  should have its bill in contact with the membrane and its head under its right wing. If it is in a different position it is malpositioned and is more likely to require assistance.
    • If necessary, a small incision can be made in the air cell membrane, over the chick's bill, to assist internal pipping.
    • The endoscope can be used to monitor the absorption of the yolk sac, to help decide, while assisting hatching, when to remove the chick from the shell. 
  • (P4.1999.w1)
  • See: Management of Hatching Bird Eggs (Techniques)

Radiographic diagnosis

  • This is a simple procedure which can be carried out at low risk to the chick and low cost. (P4.1998.w2)
  • At ICF, this is carried out once cranes show signs of weakening movement or vocalisation, or become 24 hours behind the expected hatching schedule. (P4.1998.w2)
  • Mammography cassettes, screens and films are used, with an equine radiography unit (Collimax MinXray 210, Collimax Corp., Tokyo, Japan). (P4.1998.w2)
  • The egg is placed horizontally on the cassette. An "x" label is attached to the shell at the lowest point of the aircell and 90 degrees around from this an "o" label is attached. Four views are taken, with the egg rotated 90 degrees between each view to give a relatively complete three-dimensional image of the embryo, showing the embryo's position in the egg and allowing identification of bony abnormalities. (P4.1998.w2)
    • Note: For interpretation of the radiographs it is important to know normal avian embryonic development and to have data on the incubation and hatching duration for the particular species. (P4.1998.w2)
    • Experience gained by radiographing normal eggs and by necropsy of eggs which have failed to hatch can improve interpretation of the radiographs. (P4.1998.w2)
  • This procedure has been successful in identifying malpositions such as the chick's head being at the small end of the egg, and the head being to the left.
    • Hatching assistance has resulted in survival of some of the malpositioned chicks. (P4.1998.w2)
  • In one chick a severe beak deformity preventing internal pipping was identified. (P4.1998.w2)

Assistance at hatching

  • Assistance which may be given includes making an air hole in the shell if the chick fails to pip at the expected time; moistening the inner membrane of the egg when this drying and restricting a chick during hatching; suturing if the chick's yolk sac has not fully retracted. (P87.4.w1)
Associated techniques linked from Wildpro

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Authors & Referees

Authors Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee  

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