Page 75 - Small Animal Clinical Nutrition 5th Edition

Macronutrients 75

pounds in addition to short-chain fatty acids, including accurately represent the total fiber in a pet food. Total dietary
VetBooks.ir biotin, vitamin K, carbon dioxide and methane. In cases in fiber may be a better measure for weight-management foods.
which short-chain fatty acids are absent (parenteral nutrition,
DIARRHEA AND CONSTIPATION
partial bowel resection), the colonic mucosa atrophies,
becomes inflamed and has decreased resistance to bacterial Fiber normalizes intestinal water content, absorbing water in
translocation. However, excessive fermentation and produc- cases of diarrhea and adding moisture in cases of constipation
tion of short-chain fatty acids may be accompanied by flatu- (Case 5-1). Moderate amounts of either slowly fermentable or
lence, abdominal distention and diarrhea. The rate and extent rapidly fermentable fiber possess this water-modulating fea-
of fiber fermentation in the large intestine are important ture. The more fermentable fibers (e.g., gums and soy fibers)
aspects of overall digestion and absorption of ingested nutri- can help pets with diarrhea and constipation by moderating the
ents. Short-chain fatty acids are an important energy source water content of the stool, thereby making a watery stool drier
for cattle and horses (i.e., supply up to 75% of DER); howev- and a dry stool moister.
er, they provide less than 5% of the energy needs of dogs and The binding and gelling properties of fiber also assist in
cats because of the short intestinal tract and relatively fast managing diarrhea because the increased viscosity of the diges-
transit time in these species (Brody, 1994). ta is associated with slower transit and delayed gastric empty-
ing. In constipated pets, fermentable fibers increase stool
Importance of Fiber in Foods for Dogs and Cats weight and moisture content, softening the stool.
Research results demonstrate the need for some fiber in foods Imbalances in the gut flora have been linked to diseases such
to maintain health and optimal function of the entire GI tract, as allergies, inflammatory bowel disease and diarrhea. Prebiotic
but especially for colonocytes (BNF, 1990). In people, dietary fibers, in particular, can help restore or maintain a healthy bal-
fiber has been used to help manage diabetes mellitus, obesity, ance of beneficial bacteria and prevent pathogenic organisms
gallstones, hypercholesterolemia, irritable bowel syndrome, from increasing and contributing to disease conditions.
constipation, colonic diverticulosis, colorectal cancer, celiac dis-
ease, Crohn’s disease, migraine headaches, hyperactivity in chil- DIABETES MELLITUS
dren and dental caries (BNF, 1990). Postnatal and age-related Management of diabetes mellitus in people, dogs and cats
changes in bacterial flora can affect health and resistance to dis- includes dietary changes. The glycemic index is a ranking of
ease (Buddington, 2003). A study of microflora in dogs showed carbohydrates based on their effect on blood glucose. Both
that potential pathogens such as Clostridium perfringens are slowly and rapidly fermentable fiber types help control blood
present in increased numbers in elderly animals (Benno et al, glucose levels in diabetic animals (Nelson et al, 1991; NRC
1992). However in cats, use of prebiotic fibers decreases con- 2006). Inclusion of fiber or changing carbohydrate sources can
centrations of pathogens, including C. perfringens (Terada et al, affect the glycemic index of the food. Clinically, pet foods that
1993). Different types and specific levels of dietary fiber can be contain cellulose, soybean hulls or peanut hulls minimize
important in overall therapeutic management of specific disease blood glucose fluctuations, which can reduce or eliminate the
conditions in dogs and cats. need for insulin therapy (Chapter 29). In addition, sorghum
and barley resulted in lower insulinogenic responses than rice
OBESITY AND BODY WEIGHT in dogs and cats (Sunvold and Bouchard, 1998; Bouchard and
MANAGEMENT Sunvold, 2000).
A pet food containing slowly fermentable fiber can be very
effective for controlling body weight and treating obesity Metabolism
(Chapter 27). Slowly fermentable fibers, such as cellulose or Fiber is enzymatically degraded by intestinal microbes, includ-
peanut hulls, increase bulk in the stomach and intestines and ing bacteria, fungi and protozoa but not by intrinsic mucosal
help promote a feeling of satiety when fewer calories are con- digestive enzymes.These microbes normally reside in the lower
sumed (Jewell and Toll,1996).Pets in weight-control programs small intestine and large intestine and are referred to as anaer-
can eat more total food when the calories are diluted by fiber; obes or facultative anaerobes because they can live without oxy-
thus, the dog or cat eats fewer calories and loses weight. Studies gen. They survive by producing energy through fermentation.
have shown that mixed fibers can also promote weight loss Microorganisms colonizing the lower GI tract are similar to
through several possible mechanisms including gastric disten- those found in the rumen. The proportion of different bacteri-
tion that stimulates cholecystokinin secretion, delayed gastric al species is related to the type of fermentable substrate avail-
emptying and longer ileal transit time. However, the ratio of able. Different substrates facilitate the growth of different
slowly to rapidly fermentable fiber types is important species. End products of different substrate and microbial com-
(Kritchevsky, 2001). If rapidly fermentable fibers are included binations result in formation of different levels of short-chain
in the food at high enough levels to promote satiety, adverse fatty acids (e.g., acetate or butyrate) and/or the formation of
effects such as loose stools and excessive gas may occur (Fahey gases such as hydrogen or methane.
et al, 1990). The amount of fiber in the food can be analyzed Fermentation is the energy-yielding breakdown of nutrients
several different ways. (See Analyses below.) Because the crude such as sugar, starch and fiber in an environment with little or
fiber analysis underestimates fermentable fiber, it does not no oxygen. In this process, microbes only partially use the total