Animal nutrition in zoos

Abstract

Animal health requires attention to many factors including biology, social interactions, behaviour, housing characteristics, genetics, reproduction, preventive medical care and nutrition. Nutrition in zoos is a special challenge, because there are hundreds of species to consider each representing another digestive strategy for a particular ecological niche. Feedstuffs in the wild vary extremely from region to region, from species to species and the animals have adapted their digestive system to the specific type of food. Under captive conditions, animals have to be fed with a substitute diet. In order to formulate such a diet in the zoo, many factors have to be taken into account. The first and most important aspect, however, is to consider the animal’s dietary habits in the wild. In most cases, the best alternative is to adapt the animals to diets designed for domestic livestock and pets with respect to their natural behaviour. However, seasonal variations of food intake of some species should also be kept in mind when designing a diet. Other important considerations are the possibilities given in the enclosure for natural behaviour during food intake, and the needs of related species, whose requirements are known. Finally, it is also essential to know what the animals really eat. Are they fed in-groups or individually? Is there a dominant animal that keeps the others from eating the amount they need? Many aspects in nutrition are linked to animal health. This is of great importance for the veterinarian, since it is possible to improve animal health by checking diets in reasonable intervals and observe the well-being of the animals. Factors like energy and protein requirements in reference to overnutrition and seasonality in many species are one of the great challenges in zoo animal nutrition. Obesity is one of the major problems found in zoo animal population. Many birds, like parrots are fed improperly with a diet high in energy, and therefore develop obesity. Already one peanut too much per day can change the weight of a parrot. Another problem of obesity is that it results in other diseases depending on the species and the actual overweight the animal has. These diseases are even more problematic and sometimes lead to damages that are irreversible e.g. diabetes mellitus, heart diseases and sometimes even foot problems are very difficult to heal. A body condition scoring, which is of course not available for every species needs to be established or adapted from other species. If a veterinarian or a nutritionist is able to control the animals regularly with a body condition scoring, many diseases can be prevented. Other health troubles closely associated with obesity are problems of reduced reproduction. It is also a financial problem depending on the species, since the visitor numbers rise and fall with the number of offspring a zoo can present. To solve these problems energy and nutrient requirements have to be established for the zoo population. In addition, behavioural enrichment needs to be supported, so that the animals increase their activity. Protein is another important component of the diet on which veterinarians need to have a closer look. Especially in the animal groups with a high variety in animal species like birds and reptiles little information about protein requirements can be found in the literature. It has been shown in some bird species that protein requirements are much lower than it was thought. Also a high correlation of high protein contents in diets of hoofstock and copper defiency has been found (Dierenfeld et al., 1997). Furthermore, high protein diets have been linked to diarrhea and other problems of the intestinal tract. These have also been associated to high protein in combination of low fiber diets. Many other factors like seasonality in diets is not really understood nor widely respected in zoo animal nutrition. Many other diseases in zoos are associated with dietary management. It is very difficult to give recommendations for zoo animals since little data are available for many species. Many recommendations are adapted from domestic livestock and pets. A very good example are the Vitamin A recommendations for exotic birds. The recommendations for laying hens are between 6000-8000 IU/kg DM, whereas the Vitamin A requirements for exotic birds are sufficient with 4000 IU/kg DM. Of course, many exceptions can be found e.g. the white canary which needs much more Vitamin A (10’000 IU/kg DM). Furthermore the minerals play an important role in neonatal development, clinical imbalances and maybe also sperm motility. Especially, clinical imbalances have long been recognized in carnivores and insectivores. It has been discussed in herbivores recently, that an overfeeding with minerals, especially calcium, leads to gastroliths, enteroliths and uroliths.