Page 498 - Small Animal Clinical Nutrition 5th Edition

514 Small Animal Clinical Nutrition

VetBooks.ir in dogs is 9%, DM; for preventing regain of weight, the upper fed (Fahey et al, 1990, 1990a). In one study, foods containing
The recommended upper limit for dietary fat for weight loss
either 2.2 or 15.6% fiber did not produce any measurable dif-
limit is 14% DM fat.The recommended upper limit for dietary ference in satiety (Butterwick et al, 1994). However, the dogs in
fat for weight loss in cats is 10%, DM; foods for preventing this study were fed quantities of food supplying only 40% of
weight regain should contain no more than 18% DM fat. calories for adult maintenance, and this degree of caloric
restriction may have overshadowed any effect of fiber between
Fiber,Water and Air the two groups. In another study, dogs offered maintenance
There is some debate regarding the use of calorie-diluting calories from food containing 21% insoluble fiber consumed
agents in foods intended for weight management.Typical calo- significantly less food and calories than when offered equivalent
rie-diluting agents are dietary fiber, water and air. Air is some- calories from foods containing less fiber (Jewell and Toll,
times used to reduce caloric density in dry foods only. Water is 1996). These dogs also ate less food when subsequent meals
a factor in moist foods. Water and air are removed from the were offered 30 to 45 minutes after consuming the high-fiber
gastrointestinal (GI) tract and contribute only transiently to GI food, indicating a satiety effect (Jewell and Toll, 1996). Other
fill. However, dietary fiber, besides diluting calories (Laflamme reports support a satiety effect of dietary fiber in dogs and cats
and Jackson, 1995; Jackson et al, 1997; Fekete et al, 2001), (Jackson et al, 1997; LaFlamme and Jackson, 1995; Fekete et
offers several physiologic and nutritional effects. al, 2001).
Dietary fiber helps produce weight loss by diluting calories, Fiber decreases the apparent digestibility of energy-provid-
increasing satiety and limiting food consumption as a result of ing nutrients in the food by 2 to 8% (Levine and Billington,
more bulk being present during its transit through the GI tract 1994; de Haan et al, 1990; Fahey et al, 1990a; Kelsay et al,
(Levine and Billington, 1994). Fiber may also help produce 1978; Farrell et al, 1978). Fiber decreases pancreatic enzyme
weight loss by decreasing the availability of calories by interfer- activity in vitro and pancreatic lipase secretion in vivo
ing with the digestion and absorption of fat, protein and (Isaksson et al, 1982; Stock-Damge et al, 1983). Fiber also
digestible carbohydrate (Levine and Billington, 1994). Many of increases the fecal excretion of bile acids and fat (Vahouny,
the effects of dietary fiber depend on the specific type, form and 1987). It is well documented that some dietary fibers slow the
amount of fiber used. absorption rate of carbohydrate and fat, but the total quanti-
Increased levels of dietary fiber contribute to satiety via pro- ty absorbed during the entire period of digestion is not signif-
longed distention of the GI tract. Fiber types affect the dura- icantly less than the quantity absorbed from fiber-free foods
tion of gastric and intestinal distention differently. Insoluble (de Haan et al, 1990; Edwards, 1992; Nelson et al, 1991).
fibers have little effect on gastric emptying, whereas soluble Increased dietary fiber decreases the apparent digestibility of
fibers slow gastric emptying (Levine and Billington, 1994; dietary protein when fecal nitrogen is measured (de Haan et
Vahouny, 1987; de Haan et al, 1990). Although both soluble al, 1990; Fahey et al, 1990a; Kelsay et al, 1978; Farrell et al,
and insoluble fibers slow intestinal transit, insoluble fiber (e.g., 1978). However, it is unclear whether the increased fecal
purified cellulose) produces the greater effect (Bueno et al, nitrogen is from dietary protein that would normally be
1981). Thus, even though the type of fiber affects the two seg- digested and absorbed, or whether the nitrogen is from
ments of the GI tract differently, total transit time through the increased numbers of fecal bacteria, endogenous loss of
entire GI tract is increased and is approximately the same for mucosal cells or a component of the fiber itself. The effect of
soluble and insoluble fibers. dietary fiber on mineral availability depends on the specific
Besides affecting transit time, mixed fibers are thought to fiber(s) and mineral(s). In general, insoluble fibers such as cel-
promote weight loss through delayed gastric emptying, lulose are less likely to reduce mineral availability than are sol-
increased ileal transit time and increased gastric distention. uble fibers (Chapter 5).
Gastric distention stimulates cholecystokinin secretion, thus Pet owners need to be advised that increased levels of dietary
affecting appetite. However, the ratio of slowly to rapidly fer- fiber will have noticeable effects on normal defecation habits.
mentable fibers is important (Kritchevsky, 2001). Dog foods Dietary fiber increases the amount of fecal material and fre-
with mixed fiber sources provide good weight loss performance quency of defecation (Vahouny, 1987; Fahey et al, 1990a). Dogs
(Yamka et al, 2007b). fed soluble fiber produced more feces than dogs fed similar
Actual documentation of increased satiety from dietary fiber amounts of predominantly insoluble fiber (Fahey et al, 1990).
is difficult to prove in people and more so in other animals, Dogs may not tolerate beet pulp and pectin when fed in
because satiety is a subjective feeling of fullness and a lack of amounts greater than 10% (Fahey et al, 1990a) or 13% DM
desire to eat. Indirect evidence for satiety can be obtained from (Nelson et al, 1991). Pet owners should be informed that the
animals by measuring decreases in food consumption and food- quantity of feces the animal produces will probably increase
seeking activities. In people, increased intake of dietary fiber when their cats and dogs are fed foods containing more than
decreases food intake for variable periods lasting up to eight 10% DM fiber. Excessive flatus can also be an unwelcomed side
hours (Burley et al, 1987; Delargy et al, 1993; Stevens et al, effect of feeding high-fiber foods. Fiber solubility roughly
1987). Studies in dogs have produced variable results. Some equates with fiber fermentability (Chapter 5). Increased
studies in dogs showed no effect on caloric intake when foods amounts of highly fermentable fiber in a food are more likely to
containing 12 to 14% of DM as soluble or insoluble fibers were result in excessive flatulence than if insoluble fibers are used.