Page 1084 - Small Animal Clinical Nutrition 5th Edition

1128 Small Animal Clinical Nutrition

sion of gas from the blood to the GI tract. flatus.Excessive quantities of odorless gases provide a vehicle for
Regarding flatus, the rate of excretion of gas per rectum
VetBooks.ir varies greatly in people and animals. Excretion rates in people the odoriferous gases and volatiles and probably worsen objec-
tionable flatus. Onions, nuts, spices, cruciferous vegetables (e.g.,
range from 400 to 1,500 ml/day (mean 705 ml/day). People,
broccoli,cabbage,cauliflower,Brussels sprouts) and high protein
eating their usual foods, passed gas per rectum an average of ingredients often increase production of odiferous gases.
eight to 10 times per day with an upper normal limit of 20
times per day (Strocchi and Levitt, 1997). Swallowed air is Key Nutritional Factors
thought to contribute the most to gas in the digestive tract. Table 65-1 summarizes the key nutritional factors, discussed
This may be the cause of flatus commonly seen in many below, for foods for dogs and cats with objectionable excessive
brachycephalic breeds. Vigorous exercise and rapid and com- flatulence.
petitive eating situations may exacerbate aerophagia. Studies
using ultrafast computed tomography in people show that a Digestibility
mean of 17 ml of air accompanies the swallowing of 10 ml of Digestibility, especially of the carbohydrate fraction of food, is
water. In people, air introduced into the stomach can result in an important nutritional factor in patients with excessive flatu-
flatus within 15 to 35 minutes and it has been estimated that lence. Feeding a highly digestible food reduces the residues
gases can move 10 cm/second through the GI tract (Levitt, available for bacterial fermentation in the large intestine. Thus,
1980). In a study using an in vivo methodology of flatulence foods with high digestibility (fat and digestible [soluble] carbo-
assessment in dogs, flatus developed as soon as two hours post- hydrate ≥90% and protein ≥87%) are recommended for pa-
feeding (Yamka et al, 2006). tients with objectionable flatus).
A large amount of gas is formed from colonic bacterial fer-
mentation of poorly digestible carbohydrates and certain fibers. Carbohydrate
Fiber-containing foods contribute to flatus indirectly through Certain carbohydrate sources may affect flatus production in
reduced dry matter (DM) digestibility. Certain fibers (soluble individual patients. Changing the source of carbohydrate in the
or fermentable) used in pet foods are fermented by colonic food may benefit some animals (Suarez et al, 1999). Anecdotal
microflora and may contribute to flatus directly. Foods that reports in people suggest that a food in which all carbohydrate
contain large amounts of nonabsorbable oligosaccharides (e.g., is supplied by white rice reduces flatus output. Studies in dogs
raffinose, stachyose and verbascose) are likely to produce large have also shown that foods containing rice as a carbohydrate
amounts of intestinal gas (Levitt, 1980). Dogs and cats lack the source result in less intestinal gas formation than foods contain-
digestive enzymes needed to split these sugars into absorbable ing wheat or corn (Washabau et al, 1986). This suggests that
monosaccharides. Therefore, bacteria in the colon ferment animals with flatus may benefit from foods with rice as the sole
these sugars producing hydrogen and carbon dioxide. Soy- or predominant carbohydrate source.
beans, beans and peas contain large quantities of nonabsorbable
oligosaccharides (Yamka et al, 2003, 2006). Soybean meal is Protein
commonly used in pet foods as a protein source. The stachyose Dietary protein sources and amount may affect flatus odor.
and raffinose content of soybean meal is variable ranging from Changing the sources of protein in the food may benefit some
32 to 112 g/kg and 6 to 14 g/kg DM, respectively, which could patients (Suarez et al, 1999). Ammonia and volatile amines are
contribute to flatulence if they compose more than 22 g/kg of odorous and could result from microbial fermentation of food
food DM (Yamka et al, 2006). protein residues reaching the large intestine. Therefore, protein
Diseases that cause maldigestion or malabsorption are often digestibility (discussed above) and amount should be consid-
associated with excessive flatus because excessive amounts of ered if flatus is a problem. Dietary protein should probably not
malassimilated substrates are delivered to the colon where bac- exceed 30% for dogs and 40% for cats DM. Leguminous pro-
terial fermentation occurs. Flatus may be present in animals tein sources such as soybean meal should be avoided in pets
with lactose intolerance. with excessive flatulence.
The interaction between hydrochloric acid and alkaline food
and saliva produces carbon dioxide in the stomach. The reac- Fiber
tion between gastric acid and pancreatic bicarbonate in the Soluble or fermentable fiber-enhanced foods may contribute
duodenum also generates carbon dioxide. In addition, carbon to excessive flatus in some patients. Soluble fibers including
dioxide enters the GI tract via diffusion from the blood. fruit pectins and gums (e.g., guar gum, carrageenan) are read-
Belched gas is largely swallowed air (nitrogen and oxygen) plus ily fermentable by gut microbes resulting in gas production
variable quantities of carbon dioxide. (Chapter 5). Even some mixed fibers in adequate amounts
Odorless gases (i.e., nitrogen, oxygen, carbon dioxide, hydro- (brans, soy fiber, soy hulls, pea fiber and beet pulp) can be a
gen and methane) compose as much as 99% of flatus (Strocchi source of flatulence. Some of these sources of fiber also contain
and Levitt, 1997). The residual 1% is composed of odoriferous non-fiber ingredients that can contribute to objectionable fla-
gases that contain sulfur, such as hydrogen sulfide, methanethi- tus (e.g., soy hulls and pea fiber). For patients with excessive
ol and dimethylsulfide (Roudebush, 2001; Collins et al, 2001). flatus, the amount of fiber should probably be limited to no
These gases contribute the objectionable odors associated with more than 5% DM.