Biomedical Engineering Reference
In-Depth Information
are enjoyed by the target animal but are offered in an
array of presentations. This is especially important if
dietary items need to be limited for any reason. The
enrichment portion of the diet can dilute the nutrient
composition of the consumed diet, especially if produce is
included. This must be taken into consideration when the
diet is formulated. It is a safe assumption that the
enrichment portion will be more readily consumed than
the base diet; therefore, the amount of enrichment food
offered must be appreciably below the dry matter intake
ability of the animal to ensure adequate intake of the base
diet. It may also be advisable to offer enrichment items at
differing times than the base diet to ensure complete
consumption of the base diet prior to consumption of
enrichment items.
The nutrient contribution of all foods included in the
enrichment portion of the diet must be accounted for in the
overall diet. Ideally, foods used for training and to hide
medications should come from the enrichment portion of
the diet. It is often helpful to allocate a portion of the
enrichment diet specifically for training and/or medication.
This allows greater flexibility by the caretaker to use foods
that motivate the animal or best hide the medication
needed.
Information on wild diets may be more appropriate to
inform the enrichment portion of the diet.
General Nutrition Concepts and Terms
There are many ways to express the nutrient requirements
of an animal and to express the nutrient content of food.
Human nutrient requirements are usually stated as an
amount needed to be consumed per day. For example, the
dietary reference intake (DRI) recommended intake of
protein is 56 g/day for adult men and 46 g/day for adult
women, unless the women are pregnant or lactating, in
which case it increases to 71 g/day. The requirement may
also be expressed on a body weight basis, to account for
different needs due to different body size. In the protein
example, the difference in recommended protein intake
between adult men and women merely reflects the differ-
ence in the reference weight for adult men (70 kg) and adult
women (58 kg). The recommended protein intake on
a body weight basis is the same for adult men and
nonpregnant, nonlactating women (0.8 g/day per kg of
body weight).
In animal nutrition, the requirements are usually stated
in terms of a percentage of the diet, either on a dry matter
basis or on a per energy basis. Thus, the NRC (
National
Research Council, 2003
) recommends that diets for
nonhuman primates contain 15
e
22% protein on a dry
matter basis. Because it is generally assumed that animals
will feed to satisfy their energy requirement, nutrient
density is often expressed as percent of metabolizable
energy. The assumption is that by ensuring that nutrients
are in the diet at a certain concentration, intakes for most
nutrients will be appropriate as long as energy requirements
are met. This assumption may not be true for geriatric
animals, as they often have reduced food intake, and in food
restriction studies, where a caloric restriction may also
result in other nutrient deficiencies unless nutrient
concentrations in the diet are modified.
The amount of food that a typical member of a species
can eat in a day is dependent on total gut volume and the
passage rate of digesta through the gut. In general, gut
volume increases linearly with body mass among species
(
Parra, 1978; Demment and Van Soest, 1985
). In contrast,
nutrient requirements often have allometries less than one;
for example, energy requirement increases at roughly the
3
/
4
power of body mass. Thus, small animals either need to
consume a higher proportion of their body weight in food
each day, or they need to consume foods that have higher
nutrient concentrations. Establishing the dry matter intake
ability of the species is essential when formulating animal
diets. If this aspect is overlooked, the amount of food
offered can exceed an animal's intake ability and the
consumed diet is likely to be out of balance nutritionally if
many food choices are offered. Use of published values is
Informational Resources
Unfortunately there are few rigorous studies of nutrient
requirements for most nonhuman primate species. The
rhesus macaque is the best known to date. Humans may be
appropriate models for many primate species. Indeed,
much of what is known about effects of nutrient defi-
ciencies on nonhuman primate species comes from studies
using them as models for human deficiency diseases.
The National Research Council Second Revised Edition
of The Nutrient Requirements of Nonhuman Primates
(
National Research Council, 2003
) contains a compilation
of the best information on the nutrient requirements of
various primate species as of 2003. The Nutrition Advisory
Group (NAG) to the American Zoo and Aquarium Asso-
ciation (AZA) maintains a website (
http://nagonline.net
)
that contains advice for feeding captive animals and tech-
nical papers on the nutrition and dietary husbandry of leaf-
eating and callitrichid primates.
Wild diets certainly provide a template that can inform
captive diets, and understanding a species' food-related
physiology and behavior will be greatly enhanced by
knowledge of the species' wild diet and foraging ecology
(
Ullrey, 1989; Crissey and Pribyl, 1997
). However,
a captive environment can produce circumstances in which
diets based on diet information from wild animals might
produce unintended poor health consequences. In most
cases, wild foods are extremely hard to obtain or even to
approximate with
commercially
available
foods.
