Digesta Passage, Fermentation, and Microbes in the Hindgut and Its Relative Contribution to the Nutrition of Cattle

Fermentation in the cecum and colon and digesta passage through the intestines were investigated in a series of experiments. Specific gravity, but not length, of inert particles affected their passage through the intestines. Passage was quickest for particles with a specific gravity of 1.17 and slowest for those with a specific gravity of 1.77. Fermentation in the cecum and colon was greatly affected by the forage to concentrate ratio; physical form of the forage had little effect. Contribution of the cecum and colon to total tract digestion of nutrients was greatest with the high grain diets. With the high grain diets, the cecum and colon accounted for up to 9, 6, 15 and 15% of total tract digestion of organic matter, starch, acid detergent fiber, and neutral detergent fiber, respectively. The high grain diets increased concentrations of total volatile fatty acids, acetate, propionate, butyrate, and lactate in the cecal contents of steers. High grain diets decreased cecal acetate to propionate ratio and ammonia concentrations but did not alter cecal pH or osmolality. Digestion of dietary components in the reticulo-rumen and small intestine was far more complete than would be expected for lactating cows, for whom both the quantity and degradability of digesta reaching the cecum and colon is expected to be much greater. Therefore, for lactating dairy cows, contribution of the cecum and colon to total tract digestion and diet metabolizable energy should increase substantially. The cecum and colon may be especially important as a site of fiber digestion in lactating cows receiving high grain diets. The microbial population of the bovine cecum reflected changes in both substrate fermented and fermentation products. Changing from a high forage to a high grain diet increased bacterial numbers and altered the bacterial population. Predominant cecal bacteria included Eubacterium cellulosolvens, E. ruminantcium, Fusobacterium species, and Bifidobacterium species. Ciliate protozoa were not detected in significant numbers, regardless of diet. Results show potential for manipulation of both the fermentation and digesta passage in hind gut of cattle by changes in diet. These alterations may be of importance to the nutrition of lactating dairy cows.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Dairy Science

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Jones, Joanne Siciliano

Contributors dc:contributor

• Murphy, Michael

• Agriculture, Animal Culture and Nutrition

Identifier

(UMI)AAI8823160

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/71735