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Site and extent of starch digestion in ruminants fed high grain diets. I. Role of ruminal protozoa. II. Mixtures of high-moisture corn and dry rolled sorghum. III. Duodenal infusions of casein
Abstract
Two in vitro experiments were conducted to study the effects of protozoa on starch fermentation and the amylolytic activity of ruminal microorganisms. In experiment 1, the in vitro rate of starch digestion increased (quadratic, P $<$.10) when urea was added in absence of protozoa but not in presence of protozoa. In experiment 2, no difference in amylolytic activity was found among protozoa, bacteria and a population of both organisms. Two experiments, were conducted to study the effects of feeding mixtures of high moisture corn (HMC) and dry-rolled grain sorghum (DRGS) on starch digestion. In both experiments, starch intake increased (Exp. 1 linear, P $<$.01; Exp. 2 quadratic, P $<$.02) as sorghum was added to the diet; Holotrichs were reduced linearly by additions of HMC (Exp. 1, P =.14; Exp. 2, P $<$.02); and total numbers of protozoa and Entodinium tended to be higher for the grain mixtures (quadratic, P =.20). In Experiment 1 conducted with steers, in situ rate of starch digestion of DRGS (P $<$.05) increased linearly (P $<$.05) as sorghum was added to the diet. In Experiment 2 conducted with sheep, ruminal starch digestibility increased (linear, P $<$.01) as HMC was added to the diet, whereas digestion in the small intestine (percentage of intake) was reduced (linear, P $<$.01). Eight sheep were used to study effects of protozoa on starch digestion in rumen and intestines. In situ rate of starch digestion of HMC (P $<$.02) and DRGS (P $<$.01) was increased by defaunation. Starch digestibility (percentage of intake) in the rumen was increased (P $<$.01) by defaunation and reduced (P $<$.01) in the small intestine. An experiment was conducted with sheep to determine the effect of duodenal infusions of intact casein on intestinal starch digestion. Starch digested in the small intestine, expressed as a percentage of that entering the intestine, increased linearly (P $<$.09) in response to casein infusions into the duodenum.
Subject Area
Animal diseases|Microbiology
Recommended Citation
Mendoza, German David, "Site and extent of starch digestion in ruminants fed high grain diets. I. Role of ruminal protozoa. II. Mixtures of high-moisture corn and dry rolled sorghum. III. Duodenal infusions of casein" (1991). ETD collection for University of Nebraska-Lincoln. AAI9129562.
https://digitalcommons.unl.edu/dissertations/AAI9129562