By Rick Kleyn, MSc (Agric), Nutritionist, Avi-Products (Pty) Ltd.
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 birds. 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 birds 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 birds into perspective.
The Human Element
It is people that keep birds in captivity and the way in which people behave towards their birds, 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” birds 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, birds 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.
In addition, we tend to feed captive birds diets that contain 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 form of modification.
Wild vs. Captive Diets
The first issue that needs to be examined is what exactly changes when a bird is held in captivity. In the wild, birds exhibit a wide range of physical, physiological and behavioural adaptations that equip them to acquire and then utilise their food. One only has to look at the wide range of specialised beaks that occur in the avian kingdom to appreciate this. (nice illustration of this in Comparative Avian Nutrition).
The food sources themselves are often a widely distributed and their availability will differ depending on the season. As a result of this, wild birds spend much of their time looking for and consuming their daily diet. The seasonality of food supply means that birds are often confronted with food scarcity, which is precisely why the 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.
Captive birds are obviously faced with feeding choices, or lack thereof, which are very different from those of wild birds. 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 and veterinarians see countless cases where the choices made by captive birds result in nutritionally imbalanced diets. Unfortunately, little scientific evidence exists in support of the notion that captive birds 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 birds in captivity also has a major impact in the way in which they should be fed. They are often 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 confound the attempts of even the best nutritionists. Firstly, many of the individuals 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 birds 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 birds that we keep could accurately be termed geriatric, as they survive long past the age that they would have survived in the wild.
What we already do and don’t know
In feeding any bird, our scientific objective is to establish exactly what nutrients it is that birds require in order to meet their requirements for their current physiological status, be that a mature adult, a rapidly growing young bird or a breeding pair. 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 species that we have in captivity has meant that we have had to rely on the work carried out on domestic birds (poultry). Poultry has undergone intensive genetic selection for growth and reproduction, and many people believe that for this reason they are not always appropriate to use as a model for wild birds. This is probably not an entirely valid argument, as most nutritional research in poultry 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 the bird.
What is of more concern is that of the few species that we have studied in detail, many nutritional peculiarities exist. For example, high iron levels in softbill diets can lead to iron storage disease (haemochromatosis) and ultimately death. How many of the species that we keep and 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 different species of birds 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 other 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.
Towards Better Captive Animal Feeding
I think it should be accepted that we can not expect captive birds 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 birds 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 80% of a bird’s 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. Another mistake that is often made is that people feed birds breakfast cereals. These products not only contain lower than expected levels of protein, but the all-important Calcium to Phosphorus balance is incorrect for avian species.
The simplest way in which to manage our collections is to measure. By weighing and recording both the birds and the feed that they eat, it is possible to manage many of the situations described above. Should a small 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 a bird 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 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 birds 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.