Perosis (Slipped Tendon) in Ducks: Causes, Symptoms, and Care

Perosis is a developmental leg disorder in young birds that affects the hock area and nearby bones, tendons, and joints. In ducks, pet parents may first notice a duckling that walks awkwardly, sits more than normal, or develops enlarged hocks and bowed legs. In more severe cases, the gastrocnemius tendon at the hock can slip out of its normal groove, which is why people often call the condition slipped tendon.

This problem is most closely linked with nutritional imbalance during growth, especially deficiencies involving manganese and choline. Ducks can also develop leg weakness and enlarged hocks from niacin deficiency, which is important because ducks need more niacin than chickens. These conditions can look similar at home, so a veterinary exam is the safest way to sort out what is happening.

Perosis is not usually contagious. It is more often a management and nutrition issue affecting one bird or multiple ducklings raised on an unbalanced ration. The earlier it is recognized, the better the chance of improving comfort and mobility with supportive care and diet correction.

The classic cause of perosis in poultry is dietary manganese deficiency. Merck Veterinary Manual describes perosis as enlargement and malformation of the leg joints and bones, with severe cases leading to slippage of the gastrocnemius tendon. Choline deficiency can also contribute to true perosis. In growing birds, excess dietary calcium or phosphorus can make the problem worse by interfering with manganese absorption.

In ducks, niacin deficiency is another major concern because ducks and goslings need more niacin than chickens. Niacin deficiency can cause enlarged hocks, bowed legs, weakness, poor growth, and trouble walking. It can look a lot like perosis, but Merck notes that in niacin deficiency the Achilles-type tendon usually does not slip from its condyles.

Other contributors include feeding non-waterfowl starter feed without proper supplementation, homemade diets that are not professionally balanced, rapid growth, poor overall nutrition, and delayed correction once signs begin. Trauma can also injure the hock, but when several ducklings show similar leg changes, nutrition and husbandry move higher on the list of likely causes.

Your vet will usually start with a hands-on exam, watching how the duck stands and walks, then feeling the hock joints and tendon position. They will also ask detailed questions about age, growth rate, feed brand, treats, supplements, and whether the bird is eating a ration made for ducks or a feed intended for chicks. That diet history is often one of the most important parts of the visit.

Diagnosis is commonly based on the combination of physical findings plus nutrition history. Your vet may look for enlarged hocks, angular limb deformity, tendon displacement, poor body condition, or signs that point more toward niacin deficiency than true perosis. If the leg is severely deformed, painful, or there is concern for fracture or another orthopedic problem, radiographs may help define the damage and guide realistic care options.

Because several conditions can cause lameness in ducks, your vet may also consider trauma, infection, toxin exposure, and other nutritional bone or muscle disorders. The goal is not only to name the problem, but also to identify whether the changes are still reversible and what level of support will give the duck the best quality of life.

Prevention starts with feeding a balanced duckling or waterfowl ration rather than relying on feed made for chicks without adjustment. Ducks have different nutrient needs, especially for niacin, and Merck lists duck niacin requirements at about 55 mg/kg of feed. Using a complete commercial ration designed for ducks is usually the safest foundation.

Avoid homemade diets unless they are formulated with professional guidance. Nutritional leg disease often develops when growing birds are fed unbalanced grain mixes, too many treats, or supplements added without a plan. Excess calcium or phosphorus can also worsen manganese-related perosis by reducing manganese absorption, so more supplementation is not always safer.

Watch ducklings closely during the first weeks of growth. Early signs such as enlarged hocks, wobbling, or bowed legs deserve prompt attention. Fast action gives your vet more room to help before the tendon slips or the bones remodel into a permanent deformity.

Good footing matters too. Dry, non-slip bedding, easy access to feed and water, and enough space to move without crowding can reduce strain on weak legs. If one duckling in a group develops leg problems, review the diet for the whole flock rather than focusing only on the affected bird.