TECHNIQUE

Oral Sedation of Waterfowl (Disease Investigation & Control - Treatment and Care)

Summary Information
Type of technique Health & Management / Disease Investigation & Control / Treatment & Care / Techniques:
Synonyms and Keywords See also:
Description N.B. Information given in this page is to be used in conjunction with the ORAL SEDATION section of within "Treatment and/or Control - Anaesthesia and Chemical Restraint", and "Bird Handling & Movement".
  • Choose an appropriate agent, calculate the dose required for immobilisation of the bird or birds, considering the potential for fatal overdose as well as the required dose for immobilisation.
  • If possible, habituate the waterfowl which are to be sedated to consuming un-drugged feed of the same type which will be used as bait.
  • Hide drug in a food item or items. N.B. ensure thorough mixing if in e.g. grain, or well hidden if inside an individual food item such as a piece of bread.
  • Give baited food to individual / make baited food available to group.
  • Monitor baited bird(s), be prepared to intervene if an individual is in difficulty e.g. becoming sedated while on water, or being attacked by other birds.
  • Collect baited birds when immobilised. Keep handling as stress-free as possible.
  • Monitor birds while sedated. Fresh water may be given (see: Gavage / Tubing of Birds) to increase rate of drug passage.
  • Release birds only when fully recovered.

Information on the use of oral sedatives in waterfowl as described in the literature follows:

Sodium amobarbital (oral, 100mg/kg in gelatine capsules) has been shown experimentally to produce incoordination by approximately 20 minutes after administration and a level of immobilisation sufficient for capture in Anas platyrhynchos - Mallard . This drug also has been used successfully for the capture of park waterfowl, when dissolved in water, mixed with grain and dried (900mg sodium amobarbital per cup of grain) for use on a group of waterfowl. Palatability did not appear to be a problem with the use of this drug, although some deaths (4 of 50 waterfowl, 8%) were reported in use in the group. It was considered that deaths could have been reduced by administering fresh water to speed drug passage and by less stressful handling. Of the remaining waterfowl, 41/46 (89%) were considered to have recovered by 8 hours after drug ingestion. The birds involved were mainly mallard-cross ducks (41), with eight other ducks and one goose (J2.8.w1). This drug has also been used successfully to capture a single injured park duck, by using treated bread as bait following habituation of the group of waterfowl to receiving the bread (B123).

Alpha-chloralose has been used by the U.S. Department of Agriculture's Animal Damage Control programme for the capture of nuisance waterfowl at a dose rate of approximately 30mg/kg body weight. Alpha-chloralose suspended in corn oil and injected by syringe into bread baits may be thrown to individual target individuals. Bread baits may also be dosed with alpha-chloralose mixed with margarine (prepared by handmixing 4 teaspoons of 70% vegetable oil margarine with 1.68g alpha-chloralose) or tablets made from alpha-chloralose. Tablets gave a reduced time to first effects (19 +/- 3 minutes, versus 28 +/- 6 minutes for the drug mixed with margarine and 36 +/-7 minutes for the drug suspended in corn-oil). Time to capture was: tablet 62 +/-7 (27 to 128) minutes, margarine 89 +/-14 (47-224) minutes, corn-oil (88 +/-9 (55-156) minutes. Numbers fully recovered within 24 hours were 9 of 12, 10 of 12 and 6 of 12 respectively, with all recovered within 28 hours. It was noted that the alpha-chloralose-in-corn-oil formulation is also effective for capture of waterfowl (and coots and pigeons) as a surface coating on corn (J1.33.w8).

A study of alpha-chloralose, methoxymol, metomidate, pentobarbital sodium, secobarbital sodium, thiopental sodium and tribromoethanol concluded that tribromoethanol was superior to other agents (J4.161.w1). The criteria for choosing a compound were that at the mean effective dose the drug should have a mean induction period no more than 15 minutes, mean immobilisation period no more than 30 minutes, mean recovery period no more than two hours, a therapeutic index of at least 3.0, induce sedation, hypnosis or anaesthesia without producing convulsive reaction at a dosage up to 100mg/kg body weight, be registered or available for registration with the USA Food and Drug Administration for use on animals that may be consumed by man, and be palatable when offered with bait. Qualified acceptance could be given if there was a longer recovery period or higher than 100mg/kg mean effective dose.The main points for the various agents tested in game-farm mallards (Anas platyrhynchos - Mallard) were as follows (J4.161.w1):

  • Alpha-chloralose. Non-barbiturate hypnotic derivative of chloral hydrate. Median effective dose for immobilisation 15mg/kg, LD50 33.73mg/kg, therapeutic index 2.25, induction period 7.0-16.0 minutes (mean 11.2 minutes), immobilisation period 3.0-32.0 minutes (mean 18.0 minutes), recovery period 6.0-7.0 hours (mean 6.5 hours). Palatable on corn (maize).
  • Methoxymol. Imidazole derivative. Median effective dose for immobilisation 24mg/kg, LD50 120.0mg/kg, therapeutic index 5.0, induction period 0.4-6.4 minutes (mean 2.4 minutes), immobilisation period 3.3-20.2 minutes (mean 9.6 minutes), recovery period 0.41.2 hours (mean 0.7 hours). Unpalatable - rejected by birds at optimal doses.
  • Metomidate. Acid-free base of methoxymol. Median effective dose for immobilisation 17mg/kg, LD50 85.0mg/kg, therapeutic index 6.0, induction period 1.3-10.5 minutes (mean 4.3 minutes), immobilisation period 2.0-19.0 minutes (mean 9.0 minutes), recovery period 0.8-3.0 hours (mean 1.8 hours). Unpalatable - rejected by birds at optimal doses.
  • Pentobarbital sodium. Short-duration barbiturate anaesthetic. Hypnotic. Median effective dose for immobilisation 22mg/kg, LD50 110.0mg/kg, therapeutic index 5.0, induction period 2.5-8.0 minutes (mean 6.2 minutes), immobilisation period 3.0-26.0 minutes (mean 15.6 minutes), recovery period 2.5-4.5 hours (mean 3.9 hours). Sudden arousal may occur due to disturbance during immobilisation. Prolonged ataxia (more than one day) may be seen.
  • Secobarbital sodium. Median effective dose for immobilisation 25mg/kg, LD50 68.75mg/kg, therapeutic index 2.75, induction period 1.5-7.0 minutes (mean 3.7 minutes), immobilisation period 12.0-53.0 minutes (mean 23.0 minutes), recovery period 3.5-5.0 hours (mean 4.3 hours). Unpalatable at optimal dose. Sudden arousal, often due to disturbance. Violent wing beating when administered at LD50, and convulsions in one bird at that dosage. Unpalatable at moderate to high concentrations.
  • Thiopental sodium. Short duration barbiturate anaesthetic. Median effective dose for immobilisation 54mg/kg, LD50 270.0mg/kg, therapeutic index 5.0, induction period 0.8-5.0 minutes (mean 2.4 minutes), immobilisation period 4.0-53.0 minutes (mean 24.0 minutes), recovery period 2.0-6.0 hours (mean 3.4 hours). Relatively long recovery period. Possible complications from stored residues in fat
  • Tribromoethanol. Halogenated alcohol. Median effective dose for immobilisation 100mg/kg, LD50 400mg/kg, therapeutic index 4.0, induction period 1.3-5.0minutes (mean 2.4 minutes), immobilisation period 5.0-13.0 minutes (mean 8.7 minutes), recovery period 0.4-2.0 hours (mean 1.3 hours). Ducks usually remained sitting, but often with head on floor, therefore potential drowning risk (J4.161.w1).

In wild mallards (Anas platyrhynchos - Mallard):

  • Tribromoethanol. Median effective dose for immobilisation 158mg/kg, LD50 402.0mg/kg, therapeutic index 2.5, induction period 2.0-10.8 minutes (mean 5.0 minutes), immobilisation period 7.0-39.0 minutes (mean 17.9 minutes), recovery period 2.5-3.0 hours (mean 2.8 hours) (J4.161.w1).

(J1.33.w8, J2.8.w1, J4.161.w1, B36.4.w4, B123)

Appropriate Use (?)
  • Capture of free-ranging waterfowl in a situation where physical capture methods are impractical.
  • May be used to catch an individual bird for treatment.
  • May be used to capture a group of birds e.g. during disease control operations.
Notes
  • There is little data on the effects of orally administered immobilising agents on behaviour, physiology and survival.
Complications/ Limitations / Risk
  • Possible overdose if a bird eats a large quantity of drugged bait.
  • Possible underdose if bird consumes only a small amount of drugged bait.
  • Underdosing and overdosing may occur if the drug is not thoroughly mixed with the bait.
  • Individuals may vary in their response to sedatives depending on dose, age, sex, health status and degree of stress.
  • Waterfowl may become sedated while on water and drown due to inability to keep their heads out of water.
  • Sedated birds may be attacked by other individuals.
  • Sudden arousal may occur, particularly in response to stimulation.
  • Some drugs are unpalatable at optimal concentrations.
  • Low margin of safety with some drugs.
  • Bait may be taken by non-target individual or non-target species.
Equipment / Chemicals required and Suppliers
  • Drug required for sedation.
  • Appropriate bait.
  • Appropriate capture equipment such as long-handled nets.
  • Appropriate accommodation for holding birds until fully recovered.
Expertise level / Ease of Use  
Cost/ Availability Drugs may not be readily available.
Legal and Ethical Considerations In some countries there may be legislation restricting the use of this type of technique to licensed veterinarians. For example in the UK: "The Veterinary Surgeons Act 1966 (Section 19) provides, subject to a number of exceptions, that only registered members of the Royal College of Veterinary Surgeons may practice veterinary surgery."(see: LCofC1 - RCVS Guide to Professional Conduct 2000 - Treatment of Animals by Non-Veterinary Surgeons).).

Use of Drugs (Medication):

  • Many drugs are not registered for use in particular bird species and care should be taken in their use, with proper regard for possible toxic effects. Consideration should be give to relevant legislation regarding the use of drugs.
  • In the UK, guidelines regarding the use of drugs are set out in the Royal College of Veterinary Surgeons Guide to Professional Conduct 2000: (see: LCofC1 - RCVS Guide to Professional Conduct 2000 - Choice of Medicinal Products).
Author Debra Bourne
Referee  
References J1.33.w8, J2.8.w1, J4.161.w1, B13.46.w1, B36.4.w4, B123

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