As of professional nutritionist who has worked in intensive animal agriculture for many years, my involvement at Avi-Products has exposed to me a whole new way of thinking about what I do for a living. This has been reinforced by the course in zoo and captive wild animal nutrition that I have recently completed through the University of Colorado in the United States.

We all recognise the importance of nutrition both for ourselves and our animals. Much misinformation and unfounded speculation about nutrition is disseminated through the popular press, with the worst culprits probably being advertisers. This often clouds the issue. However, what is certain is that even if captive animals are not showing obvious signs of a nutrient deficiency, marginal deficiencies of many of the nutrients lead to reduced fertility and a suppression of the immune system. In this short article I will attempt to put the nutrition and feeding of captive animals into perspective.

It is people that keep birds and animals in captivity, and the way in which people behave towards their animals, their welfare and their care are very often controlled by human emotion. We tend to behave in an anthropomorphic (giving human-like qualities to the animals) and this can be a problem in itself. People get very possessive of "their" animals and take great offence if someone tries to tell them what to do or offer corrections, particularly if they think they are doing the best that can be done.

Human beings tend to eat discrete meals and, almost without thought, have imposed a similar pattern on almost every species kept in captivity. As a result, animals are fed discrete meals at specific and predictable times, year in and year out. Diets are usually prepared according to some predetermined recipe and vary little throughout this period.

Captive animals tend to be fed on diets containing ingredients that are important in human agriculture. These would include commercially available fruits and vegetables, mass produced grains, fish species that are commercially fished, by-products of the agricultural process and livestock feeds, with or without some modification.

The first issue that needs to be examined is what exactly changes when animals are held in captivity. In the wild, birds and mammals exhibit a wide range of physical, physiological and behavioural adaptations that equip them to acquire and then utilise their food. These food sources are often a widely distributed and their availability will differ depending on the season. As a result of this, wild animals spend much of their time looking for and consuming their daily diet. The seasonality of food supply means that wild animals are often confronted with food scarcity, which is precisely why nutritional costly process of breeding is confined to times of the year where food is abundant. Captivity removes much of the complexity and seasonality of food resources. Normally, the condition of wild animals will change with season, but captive animals are mostly fed enough to remain in "good" condition throughout the year.

Captive wild animals are obviously faced with feeding choices, or lack thereof, which are very different from those of animals in the wild. There is little reason therefore to suppose that the choices made in captivity bear any resemblance to the choices that are made in the wild. On the contrary, nutritionists see countless cases where the choices made by captive animals’ result in nutritionally imbalance diets. Unfortunately, little scientific evidence exists in support of the notion that captive animals posses "nutritional wisdom" that enables them to select diets that are appropriate for their needs.

The way in which we keep and manage birds and animals in captivity also has a major impact in the way in which they should be fed. Captive animal populations often comprise mixed groups. That is animals and/or birds that are kept in groups of different ages or physiological states (breeding versus non-breeding birds) and/or in groups of mixed species.

These mixed populations of birds and animals confound the attempts of even the best nutritionists. Firstly, many of the individuals in an enclosure have completely different nutritional requirements. Secondly, very clear pecking orders become established both within a species and between species. This represents another reason why the argument that animals are able to select what they require will mostly not work in a captive situation. Simply put, those at the top of the pecking order will often consume all of the "favoured" items. Wild fruits are generally higher in fibre and not as sweet as modern fruit cultivars. As many species are know to develop a sweet tooth, those individuals at the top of the pecking order mostly eat a high sugar diet and become obese, while the less aggressive individuals often go hungry.

Until such time as we are able to reproduce the seasonal, spatial and nutritional complexity of the diets found in the wild, captive animals will be faced with choices that they have not been evolved to make. For this reason, it will remain the prerogative of the humans that keep animals to make these choices on their behalf.

Another feature that is probably unique to captive populations, is that many of the animals that we keep could accurately be termed geriatric, as they survive long past the age that they would have survived in the wild.

In feeding any animal, our scientific objective is to establish exactly what nutrients it is that the animals require in order to meet their requirements for their current physiological status, be that an adult being maintained, a young growing individual or a breeding animal. Through the rapid development of nutritional science during the last century, we know that we need to meet the requirements for between 40 and 50 different components of the diets, which are termed nutrients.

The paucity of nutritional information available for most of the wild species that we have in captivity has meant that we have had to rely on the work carried out on domestic animals. These animals have however undergone intensive genetic selection for growth and reproduction, and many people believe that for this reason domestic animals are not always appropriate to use as a model for wild animals. This is probably not an entirely valid argument, as most nutritional research in domestic animals is published in a systematic way. That is to say, we know how much protein and energy is required to produce a gram of egg or a gram of muscle tissue. We also know what the impact of size and insulation (feather cover) has on the maintenance requirements of animals.

What is of more concern is that of the few species that we have studied in detail, many nutritional peculiarities exist, some examples of which follow. Guinea pigs require that we add Vitamin C to their diets in that they are unique in that they do synthesise their own Vitamin C, as do most other species. Many softbill birds (frugivours) are known to be highly sensitive the high levels iron in their diets. The domestic cat is known to have a high requirement for Taurine. How many of the captive animals that we feed have similar nutritional peculiarities is hard to know, as much research still needs to be carried out.

It would be true to say, that the similarities between the nutritional requirements of animals are far greater than the exceptions. It should be remembered that the differences from within the population of one species are often greater than any differences that occur between species. I believe that the right thing for nutritionists to do is to borrow information known about domestic species and apply it to captive wild species. I accept that as a model this may not be entirely correct, but it is better to use a model that is slightly flawed than it is to do nothing at all.

I think it should be accepted that we can not expect captive species to balance their own diet, which places them firmly in the hands of their keepers. Balancing and then preparing a diet is not as straight forward as it seems. It takes time, specialist knowledge and a wide range of ingredients. Nutritionists see as many animals that have been overfed or supplemented as they do animals that are showing deficiency symptoms, which attest to just how difficult it is to get the balance correct. Sadly, the first symptom many bird owners see when an imbalanced diet is fed is a failure to breed successfully.

Prof. Nancy Irlbeck from the University of Colorado believes that a balanced diet can only be achieved by feeding a high proportion of the total feed intake as a complete feed. She believes that if possible, mammals should receive at least 50% of their feed in the form of a balanced feed, be it in the form of Antelope Cubes or Primate Biscuits, and that at least 80% of a birds daily intake should comprise a balanced diet. The remainder of the diet can be in the form of nuts, fruit and vegetables or insects.

Many people incorporate pet food into their feeding programs as the "complete" part of the diet. Dog and cat food is designed to meet the nutrient requirements of carnivores, and they often contain high levels of calcium, phosphorus and most importantly for birds iron. High iron levels in softbill diets can lead to iron storage disease (haemochromatosis) and ultimately death.

The simplest way in which to manage our collections is to measure. By weighing and recording both the animals and the feed that they eat, it is possible to manage many of the situations described above. Should a small mammal or bird loose weight, it is simply not eating enough, and some method needs to be devised to ensure that either it’s diet is changed or it is fed in a different manner. On the other hand, if an animal is gaining weight, the only way in which to prevent it is to reduce its energy intake, or to increase it’s level of physical activity.

It is true that we do not know exactly what the nutrient requirements of many of the species that we keep are. However, through the application of sound nutritional principles, based on the similarities between species rather than the differences, it is possible to achieve a far higher health status and level of breeding success in a collection. Most good international zoos now employ qualified nutritionists to ensure that their animals are being correctly fed.

As a nutritionist, it is sad to see that much of the science and knowledge we have to offer is given scant regard. Remember that all of the animals and birds that we feed are valuable, either in terms of their monetary value, their endangered conservation status or simply because we love them. This is precisely the reason why we often kill our animals with kindness by feeding them too much of the wrong foods.

While it may be difficult to match those conditions that are found in the wild, it is not difficult to do a reasonable job of meeting the nutrient requirements of our collections, if we simply apply the basic principles of sound nutrition. Avi-Products has 4 qualified and experienced nutritionists in its employ, and we are always available to help people when it comes to the correct feeding of captive species.