Waterfowl husbandry and medicine (Proceedings)

Taxonomy

Waterfowl belong to the order Anseriformes which has 2 families; Anhimidae (screamers) and Anatidae (ducks, swans, and geese). This section will concentrate on Anatidae. Anseriformes have been domesticated since 2500 BC.

Anatomy and Physiology

Anhimidae

          • South American birds; unwebbed feet, hooked bill; gradual feather molt

Anatidae

Annual or biennial molt

          • Most ducks molt 2x/year and the breeding (nuptial) and non-breeding (winter or eclipse) plumage are distinct. Their plumage may have iridescent colors. Most swans and geese molt 1x/year and all the flight feathers are shed almost simultaneously so birds are unable to fly for 3-8 weeks. Their plumage lacks iridescent colors. All species have a highly developed uropygial (preen) gland

Broad or conical bill with serrated lamellae

          • The bill of ducks has "nail" at end of top beak to facilitate grasping slippery objects and also lamellae along edges to cut or filter food

Bristled tongue and lateral margin processes

          • Interdigitate with the bill lamellae

          • Allows for straining and retention of food particles

          • Facilitates cropping of vegetation

Bill tip organ at tip of upper and lower bill

          • Contains mechanoreceptors = Herbst's corpuscles; bill tips are extremely sensitive

          • Assist with food gathering

Osmoregulation

          • Nasal salt gland dorsal to the eye:Duct opens into the rostral nasal cavity; well-developed in species living in salt or brackish water; salt is extracted from blood and flows as a thick liquid to the bill tip

          • Retroperistalsis of urine from the ureter into the coprodeum and distal GIT; additional water resorption before excretion

Musculoskeletal

          • Totipalmate (all four toes are connected by webbing) and are really designed for swimming, not for walking.

          • Excavated cavity in the cranial sternum: swans; contains elongated tracheal coils

          • Swans have the most ribs (9 attached pairs) and cervical vertebrae (25)

Respiratory

          • syringeal bulla: male ducks; asymmetrical distension of the left syrinx; involved in vocalization

          • Nares communicate

Reproduction

Generally lay 3-10 eggs/clutch with an incubation period that ranges from 21-44 days, depending on species. Their chicks are precocious and can swim, walk, and feed themselves almost from birth. They are born covered in down and fledging usually occurs at 30-90 days. They have a relatively long life span; approximately 10+ years for ducks and 25+ years for geese and swans. The clinical chemistry values vary with species and should also be evaluated with respect to age, sex, and reproductive status of bird. Sexual Maturity: -Ducks approximately 1 year of age; Geese usually 2 years of age; -Swans about 5 years. Gender determination: -Ducks usually sexually dimorphic (except for some species such as Pekin); Swans and geese usually sexually monomorphic; Males of all species have an erectile phallus

Husbandry

It is important that waterfowl have access to water to swim in or they may develop feet and leg problems or other diseases. Bumblefoot is a common problem in waterfowl. They should also have as large an enclosure as possible with access to both shade and sunlight.

Typical set-up: large, open enclosures with a large pond

     o Pond size is important

     o minimum depth = 2 feet most species

     o minimum depth = 4 feet for diving species

     o gradual slope, islands, partial shading

     o contamination may lead to poor water quality and disease

     o cold water, aerators, replace water by draining and filling

     o warm ponds + organic matter = increased risk for botulism

     o cultivate and reseed resting places every 6-12 months

     o nylon enclosures limit unwanted wild birds

Hospital set-ups:

     o concrete pool with gradual slope

     o soft flooring or mats

     o adequate ventilation

Nutrition

Varies based on species, reproductive status, and age. There are commercial waterfowl feeds produced that are appropriate for all life stages. Starter rations (19-22% protein) should only be used up until 3 weeks of age. Goslings should be supplemented with greens or grass clippings. Grower rations (16-17% protein) can be used in birds intended for the meat market until 8 weeks in ducks and 15 weeks in geese. For birds not intended for meat, go from the starter ration to a developer ration (12-14% protein) at 3 weeks and switch to a maintenance ration when fully grown. Breeder or layer feeds (17-18% protein) should only be fed 1-2 weeks prior to laying. Avoid medicated feeds intended for poultry. Waterfowl need to have fresh water always available near food. With hospitalized patients, adding food to water may stimulate interest in feeding. Water is necessary to facilitate swallowing and should always be available. Geese are grazers and need grass or hay in addition to pelleted diet.

Restraint

Restraint technique

     o cradle bird under one arm against handler's body:

     o head pointed backward; support body weight and restrain the wings

     o do not lift by wings; peripheral nerve damage

Surgery and anesthesia

Inhalants (isoflurane/sevoflurane) preferred

     o respiratory depression more severe in ducks than mammals

          • intubate, assisted ventilation

     o mask induction of diving species

          • bradycardia and apnea that persists for several minutes

          • not a true diving response; stress response

               » mediated by trigeminal nerve receptors in beak and nares

               » produces a potentially dangerous anesthetic state

          • premedication with midazolam recommended to reduce this response

Field procedures may require use of oral or injectable anesthetics

     o alpha chloralose, tribomoethanol

          • mixed with feed to facilitate capture

          • low therapeutic index

               » high potential for overdose, drowning

     o injectable produce more severe side effects and mortalities than inhalants

               » propofol in canvasback ducks and mallards

               » cardiac arrhythmias, apnea, ventilation (mallards)

               » respiratory depression, low therapeutic index (canvasbacks)

Infectious diseases

     o free-ranging anseriformes

          • common agents causing clinical disease

               » duck plague

               » avian cholera, Pasteurella multocida

               » aspergillus, Aspergillus fumigatus

          • free-ranging anseriformes as reservoirs

               » avian influenza A virus

               » Newcastle disease virus

               » yersiniosis, Yersinia pseudotuberculosis

               » chlamydiosis, Chlamydia psittaci

          • unknown prevalence and clinical significance

               » mycoplasmosis, Mycoplasma anatis

               » poxvirus

               » tuberculosis, Mycobacterium avium

     o captive anseriformes

          • common diseases causing clinical signs

               » tuberculosis, Mycobacterium avium

               » aspergillosis, Aspergillus fumigatus

               » salmonellosis

               » duck virus hepatitis (picornavirus)

          • less common diseases

               » yersiniosis, Yersinia pseudotuberculosis

               » erysipelas, Erysipelothrix rhusiopathiae

               » chlamydiosis, Chlamydia psittaci

               » mycoplasmosis

               » poxvirus

               » avian influenza A virus

Miscellaneous diseases of waterfowl

Most common health problems associated with backyard waterfowl are related to inappropriate husbandry, nutritional problems and other less common syndromes as listed below. Foreign body ingestion, predation, interspecies aggression and competition and neoplasia should also be considered common reasons for the presentation of captive Anseriformes.

Amyloidosis:

General term that referring to diseases or lesions characterized by deposition of amyloid, which is a pathologic proteinaceous substance that compresses the cells in organs and essentially "clogs them up". This causes the liver, spleen, or other affected organs to fail and is a common cause of death. The pathogenesis is poorly understood, but may be related to stress.

Nutritional:

In young birds, most musculoskeletal deformities are a result of improper diet and exercise.

Perosis ("slipped tendon"):

Deformity of the hock and medial luxation of the Achilles tendon that may be caused by manganese deficiency. Must usually be surgically repaired.

Angel Wing:

High energy or protein diets causing excessively fast growth in young anseriformes. This leads to valgus deformity (lateral rotation) at the carpal joint. Figure-8 banding may be used to treat successfully in the first few days, but if left too long will become permanent deformity.

Rickets:

Lack of vitamin D leading to bone deformities.

Hypovitaminosis

A: captive and free-ranging birds fed strictly on grains through winter. Clinical Signs: ducklings: ataxia, poor growth, paresis, paralysis, death; Adults: white nodules in esophageal mucosa, cachexia

Niacin deficiency:

Vitamin B6 deficiency; Clinical signs: leg deformities, bowed legs, weakness, poor growth. Captive birds, ducklings have a higher requirement than other avian juveniles. Treatmetn: Vit B parenterally followed by correcting nutritional deficiency through balanced diet.

Pododermatitis:

"Bumblefoot" lesions characterized by bacterial dermatitis of the plantar surface of the feet. Often related to inappropriate surfaces, obesity, poor hygiene or a combination of factors. Treatment includes managing the inciting cause and should be followed as with other pododermatitis. Culture and sensitivity of colonizing organism is paramount to dictate antimicrobial therapy.