In the wild, penguins, pelicans, and other fish-eating species feed primarily on fish, crustaceans, and squid. These food sources vary in fatty acid, vitamin, and carbohydrate contents. In captivity, piscivorous birds are commonly fed squid, smelt, herring, mackerel, and whiting. One of the most important aspects of feeding piscivorous birds is fish quality.
Feeding several fish species is advised to prevent nutrient deficiencies, although in some cases, one species of fish has been fed for a lifetime. Captive seabirds develop strong preferences for a particular fish if it is fed exclusively for prolonged periods, which can lead to both nutritional deficiencies and inanition if the feeder fish becomes unavailable. Fish should be in good condition, not emaciated.
Supplements commonly given to captive penguins include vitamins A, D, B1, and E. The need for supplementation and the quantity required depend on the quality and content of the primary diet. Supplements can be given to the fish as tablets, gel, or liquid injection. Vitamins B1 (thiamine) and E can be decreased while the fish is being refrigerated at −18°C or below, so supplementation of these vitamins may be necessary.
Dietary salt (NaCl, 0.5–1 g bird/day) is often provided to birds in freshwater exhibits to help maintain proper functioning of the salt glands.
Thiamine in Piscivorous Birds
Thawing fish in running water depletes them of water-soluble vitamins. Instead, fish should be thawed slowly in a refrigerator and allowed to come to approximately 10ºC within a few hours of feeding. Additionally, several fish species contain thiaminase, leading to thiamine deficiency during the defrosting process.
Supplementation of thiamine is recommended at 30–35 mg/kg fish daily (1).
Vitamin E in Piscivorous Birds
Most fish are deficient in vitamin E. Clinical signs of vitamin E deficiency in piscivorous birds include weakness and inability to stand or hold the wings in normal posture. Severe generalized myopathy with muscle atrophy, degeneration and necrosis, and replacement with fibrous connective tissue can occur with chronic, pronounced vitamin E deficiency. Supplementation with 100 IU vitamin E/kg fish daily has been proposed. However, oversupplementation (vitamin E at 500–10,500 IU/kg food) may result in decreased growth and coagulation disorders, possibly from creating vitamin K deficiency rather than directly from vitamin E toxicity.
Hand-feeding of species and individuals of concern will ensure that each bird receives the proper amount of food and supplement. Some piscivorous species will accept commercial bird-of-prey diets, trout pellets, and/or mice in the diet, as well as fish.
References
Crissy S, Slifka K, McGill P. Penguins: Nutrition and Dietary Husbandry. Fact Sheet 012. Nutrition Advisory Group; 2002.
