Biomedical Engineering Reference
In-Depth Information
two animals on different nutritional planes may be equally
healthy, however, their internal physiology, and thus their
responses to experimental conditions, may differ. Reducing
the variation in nutritional status among subjects in an
experiment may be helpful
evidence for the requirements for particular nutrients by
different species.
Purposes of Food
The primary purpose of captive primate diets must be to
meet the nutritional needs of the species. However, food is
a powerful motivational resource, and can have important
functions outside of direct nutrition. Food is often used for
enrichment and training. To ensure that the foods provided
to captive animals appropriately fulfill all these functions it
is helpful to conceive of the diet as divided into three parts:
(1) the base diet; (2) the enrichment portion; and (3)
training rewards. An additional use of food is to medicate
animals by hiding medications within preferred foods.
Partitioning the diet into these components reinforces
that all foods given to animals must be accounted for in the
dietary assessment while acknowledging the diverse roles
food plays in captive animal management. The enrichment
and training portions of the diet can dilute the nutrient
composition of the consumed diet, especially if produce
(fruits and vegetables) or high sugar content foods
comprise a significant proportion. Changes in the amounts
or types of enrichment and training foods may require an
adjustment in the base diet, and the base diet will constrain
the amounts and types of enrichment and training foods that
can be offered to animals.
The base diet should include a food (commercial
primate biscuit, canned primate food, primate gelled food,
or home-made primate formula) that is nutritionally
complete. The base diet serves a number of critical needs.
First, it provides a source of known nutrients that should be
adequate to support the nutritional needs of the animals.
Second, it provides dietary consistency, so that all animals
will be on approximately the same nutritional plane. Third,
it allows animals to be fed appropriately, quickly, and easily
in the event of circumstances which prevent offering the
entire diet. Denoting the base diet as such heightens the
awareness of the animal care staff to the importance of this
portion of the diet. The amount of the overall diet the base
diet should comprise is dependent on the species and in
some cases the individual animal. In general, the smaller
the species the higher the proportion of the overall diet the
base diet needs to be. A general rule of thumb is that the
base diet should provide at least 75% of the dry matter
intake (or of the energy intake). In theory it could constitute
the entire diet.
The enrichment portion of the diet should be as
complex as possible without compromising the overall
diet constitution and include foods that are appropriate for
the target species. Sheer number of ingredients does not
always equate to a more complex diet, especially if all
items are offered daily in the same manner. A complex
enrichment diet may have just a few different items that
to reduce the noise in the
results.
It is a truism that although animals eat food, what they
require are nutrients. Evolution has provided species with
morphological, physiological, metabolic, and behavioral
adaptations that allow them to extract nutrients from the
food items found in their environment. When animals are
maintained in captivity, the environment, including the
available food items, is dramatically different from that of
the species' evolutionary past. This has many consequences
for captive animal nutrition. It does not mean, however, that
captive diets need to mimic or even approximate natural,
wild diets. It does mean that the evolved dietary adaptations
of the species must be taken into account when diets are
formulated, as should the altered circumstances presented
by the captive condition.
Nutrients are molecules that are required for life that
cannot be synthesized by an animal but rather are acquired
by eating. They can be chemical elements (e.g. sodium,
potassium), enzymes (e.g. vitamin C, niacin), or even
steroid hormones (e.g. vitamin D). Many of the so-called
macro nutrients (those nutrients required at the highest
concentration in the diet) are classes of molecules
(e.g. protein) which are sometimes fairly complex to
describe (e.g. fiber) and in which specific molecules can
have varied functions (e.g. fatty acids). Even vitamins
(e.g. vitamins A and E, folate) can consist of suites of
related molecules all with varying levels of functionality.
Finally, most nutrients have both minimal levels that
animals must obtain and maximal levels above which
health can be compromised. In other words, many nutrients
are both required and potentially toxic.
The challenge of nutritional management of captive
nonhuman primates is to provide foods that are both
palatable and meet the nutrient requirements of the species
without providing excess calories. The evidence regarding
specific nutrient requirements for most primate species is
quite limited; still, adequate, safe levels of most nutrients
can be estimated. Nutritionally complete diets for
nonhuman primate species have been successfully formu-
lated. Thus, nutrient deficiencies in captive nonhuman
primates are unlikely to occur due to a poor understanding
of the requirements. Rather, other factors such as the
manner in which the diet is given to the animals, how it is
stored, not accounting for the quantity and quality of
enrichment and training foods, and the underlying health of
the subjects may be more consequential. Accordingly, this
chapter will focus more broadly on providing guidance for
the appropriate dietary management of captive nonhuman
primates rather than merely provide a review of the scanty
