| The overall objective of this research was to evaluate glucose-based carbohydrate sources for use in canine diets, including ingredient chemical compositional analyses, effects on apparent total tract macronutrient digestibility, and effects on fecal characteristics, microbiota composition, and fermentative end-products. Our first aim was to determine the chemical composition of carbohydrate sources commonly incorporated into pet foods. We evaluated various whole grains, processed grains, grain fractions, and pseudocereal grains. Our second aim was to evaluate the effects of graded concentrations of polydextrose on apparent total tract macronutrient digestibility, fecal characteristics, fecal fermentative end-products, and fecal microbial populations in healthy adult dogs. Polydextrose was fed at 0, 0.5, 1, or 1.5% of the diet dry matter (DM). Our third aim was to determine the effects of Resistant starches (RS), naturally from whole grains, on apparent total tract macronutrient digestibility, fecal characteristics, and fecal fermentative end-products in healthy adult dogs fed a baked whole grain-containing biscuit treat. Dogs received either 0, 10, or 20 g biscuits/d (estimated to be 0, 2.5, or 5 g RS/d) that were fed within their daily caloric allowance. Our fourth aim was to determine the effects of graded concentrations of a corn-based RS source on apparent total tract macronutrient digestibility, fecal fermentative end-products, and fecal microbial populations in healthy adult dogs. Dogs were fed 0, 1, 2, 3, or 4% of diet DM of Hi-maize 260RTM, a corn-based ingredient that consists of 60% RS and 40% digestible starch.;In our first aim, we determined that whole grains and grain fractions contain many essential nutrients including amino acids and minerals, and may provide a significant source of fiber. Because the chemical composition of grains varied greatly depending on their respective fractions (i.e., barley flake vs. malted barley vs. steamed rolled barley) and among grain type (i.e., barley flake vs. brown rice vs. canary grass seed), pet food professionals must consider both factors when formulating diets. In our second aim, we determined that polydextrose appeared to be moderately fermentable, which was evident by the increased (P<0.05) fecal SCFA concentrations, primarily acetate and propionate, and by the decrease (P<0.05) in fecal pH, without affecting food intake or fecal output. The inclusion of polydextrose also decreased (P<0.05) some protein catabolites, in particular fecal indole concentrations. Fecal C. perfringens concentrations were decreased (P<0.05) by including polydextrose in the diet, but other bacteria were unaffected. In our third aim, we determined that fat digestibility decreased (P<0.05) with whole grain treat consumption (i.e., increased RS consumption), but apparent total tract dry matter, organic matter, and crude protein digestibilities were not affected. Fecal fermentative end-products, including short- and branched-chain fatty acids, ammonia, phenols, and indoles, and microbial populations were not affected. In our fourth and final aim, we determined that dietary RS linearly decreased (P<0.05) apparent total tract dry matter, organic matter, crude protein, fat, and gross energy digestibilities, and fecal pH was linearly decreased (P < 0.05) with increased RS consumption. Fecal output was linearly increased (P < 0.05) with increased RS consumption. Fecal scores and fecal fermentative end-product concentrations, including ammonia, short-chain fatty acids, branched-chain fatty acids, phenols, and indoles were not affected by RS consumption. Predominant bacterial phyla present in all dogs included Firmicutes, Bacteroidetes, Fusobacteria, Proteobacteria, Actinobacteria, and Tenericutes. Although few bacterial taxa were altered by RS consumption, fecal Faecalibacterium were increased (P < 0.05) with increased RS consumption.;This research provided a compositional database of whole ingredient, fractionated ingredient, and single-source carbohydrate sources, which may potentially impact future pet food formulations. This research provided knowledge about the use of non-digestible, glucose-based carbohydrate sources, including polydextrose, whole grain-containing RS and dietary fiber, and corn-based RS, for use in canine diets. Based on the current results, the most prominent beneficial effects were observed in healthy dogs when fed 1.5% polydextrose. (Abstract shortened by UMI.). |
