Biomedical Engineering Reference
In-Depth Information
Carbohydrate
In general, carbohydrate serves as the main energy source
in nonhuman primate diets, in both captivity and in the
wild, accounting for approximately 65 e 75% of ME. There
is no specific requirement for carbohydrate beyond as
an energy source; however indigestible carbohydrates
(e.g. fiber and resistant starches) provide a fermentable
substrate that may contribute to colon health and appro-
priate digestive function.
fermentation, or, for colobine monkeys, fiber will be fer-
mented in their specialized, sacculated, nonacidic stomach,
referred to as fore gut fermentation ( Kay et al., 1976 ).
Whether an animal is a hind gut fermenter or a fore gut
fermenter influences the importance of fiber and its role in
nutrition and health. Because few colobine monkeys are
kept in captivity, and they are rarely if ever used in
biomedical research, this section will focus on the role of
fiber in hind gut fermenters, such as chimpanzees, baboons,
macaques, and marmosets.
Carbohydrate Sources
Carbohydrate sources may vary from simple (e.g. glucose)
to very complex (e.g. fiber). In commercial primate diets,
starch is a primary carbohydrate source as starch aids in the
manufacturing of pellets or extruded biscuits by acting as
a binding agent to hold dietary components together.
Additionally, due to the heating of starch sources during
pelleting or extrusion, digestibility of this component will
be increased compared to feeding the raw source. Typical
carbohydrate sources include sugars (generally in purified
or semi-purified diets or for palatability in commercial
diets), grains (e.g. corn, wheat, rice) which may be ground
whole or have fractions extracted, forages (e.g. alfalfa), and
byproducts (e.g. beet pulp, soybean hulls, rice hulls).
Lactose may be an appropriate choice to include in diets for
very young animals, but lactose is not readily digestible by
animals past weaning age and should generally not be fed
to animals beyond infancy.
Importance of Fiber to Gastrointestinal Tract
Health
Fiber is important for digestive function. It provides bulk in
the lower intestinal tract, retains water in the fecal matter,
and aids in the passage of digesta through the gut. These are
some of the positive benefits of insoluble fiber, most of
which are largely due to its physical properties. A lack of
fiber in the diet can result in constipation, poor stool
formation, and compromised gut motility.
Fiber also may contribute to intestinal health due to its
biochemical properties. Both soluble and insoluble fiber
will be fermented by symbiotic microflora in the gut. The
resulting short-chain fatty acids (e.g. butyrate, acetate, and
propionate) will be absorbed by the colonic epithelium and
will stimulate colonic blood flow and enhance absorption of
fluid and electrolytes ( Topping and Clifton, 2001 ). Butyrate
is a preferred fuel for colonic epithelial cells, and appears to
contribute to colon health ( Topping and Clifton, 2001;
Wong et al., 2006 ). Fiber fermentation products may
contribute in a variety of ways to intestinal health.
In the wild, many primates feed on gums, a soluble
fiber. This is especially true for the small-bodied calli-
trichid primates. The common marmoset (Callithrix
jacchus) feeds extensively on gum in its native Brazil,
which raises questions about the nutritional or physiolog-
ical reasons to feed marmosets gum in captivity.
Gums are incomplete foods, providing mainly energy in
the form of fermentable soluble fiber and minerals ( Power,
2010 ). Gums have been suggested to serve as important
calcium sources for galagos ( Bearder and Martin, 1980 )
and marmosets and other callitrichids ( Garber, 1984 ) in the
wild. The levels of calcium in gums that have been assayed
range from below 0.5% to around 1% on a dry matter basis.
These are fairly high levels for wild foods, but most man-
ufactured primate diets contain 0.8 e 1.2% calcium on a dry
matter basis. If feeding gum reduces consumption of the
nutritionally complete feed that should form the base of the
diet, then calcium intake may not be increased. In contrast,
substituting gum for fruit may indeed increase calcium
consumption. However, that increase will come at the
expense of decreasing the consumption of vitamins in fruit.
At present, there are no demonstrated nutritional reasons
Fiber
Fiber refers to a class of carbohydrate molecules found in
plants. There are many definitions of fiber. For the purposes
of this chapter we define fiber to be carbohydrate compo-
nents of plants that are resistant to vertebrate digestive
enzymes. This definition includes both plant cell wall
constituents such as cellulose and hemicellulose, and other,
often soluble fiber fractions such as pectins and gums. All
these substances are resistant to primate digestive enzymes
but can be fermented by symbiotic gut microbes (Van
Soest, 1982). In the wild, short-chain fatty acids (SCFA)
from the fermentation of fiber can provide primates with
a significant amount of their energy requirement. This is
less important in a captive setting, as energy is rarely
a limiting resource for captive primates; however, fiber and
its fermentation products provide other potential health
benefits besides metabolic energy. An increase in fiber
content in the diet led to a decrease in mean weight among
vervet monkeys ( Fairbanks et al., 2010 ), suggesting that
high-fiber diets may be beneficial to combat obesity in
some captive nonhuman primates.
Primates will ferment fiber either in the lower intestinal
tract (the cecum and colon), often referred to as hind gut
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