The order Anseriformes includes ducks, geese, and swans. These waterfowl vary from strictly herbivorous (swans, most geese, most ducks) to highly piscivorous (marine ducks, mergansers). Commercial duck or game-bird pellets should contain 14%–17% protein and 3%–6% fat with an adequate vitamin mineral supplement. During breeding season, the amount of protein can be increased to 16%–21%. In winter in colder areas, more fat can be added by adding 20% of corn to the diet. Piscivorous waterfowl consume mostly a fish-based pellet containing 25%–40% protein and 5%–10% fat. Some breeders prefer to feed a “sinking” or “floating” waterfowl pellet in the water. However, pellets fed in water should not be allowed to dissolve before consumption.
Swans and geese are fed the same diet as herbivorous ducks. Although waterfowl can live on only nutrient adequate pellets, usually some lettuce is also fed.
Diets of only bread, lettuce, and corn, which are unfortunately often provided, lead to protein and multiple vitamin deficiencies. These often manifest as poor plumage, swollen joints, and pododermatitis.
As is true for most bird species, young waterfowl should be fed starter pellets with higher fat (5%–8%) and protein (16%–20%) content. However, excessively rapid growth of large waterfowl must be avoided to prevent bone and joint deformities, such as angel wing and perosis.