J. Anim Sci.
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J. Anim Sci. 1986. 62:789-803.
© 1986 American Society of Animal Science
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Postprandial Trends in Estimated Ruminal Digesta Polysaccharides and Their Relation to Changes in Bacterial Groups and Ruminal Fluid Characteristics1

J.A.Z. Leedle2,3,, K. Barsuhn2 and R. B. Hespell3

The Upjohn Company, Kalamazoo, MI 49001 and University of Illinois, Urbana 61801

Abstract

In a diurnal study, feedstuff and digesta polysaccharides, ruminal bacterial carbohydrate-fermenting groups, and selected ruminal fluid characteristics (ruminal pH, ammonia and volatile fatty acids) were measured in ruminal-cannulated Holstein steers fed high- or low-forage diets at maintenance level intake once daily. A procedure for the sequential extraction of soluble sugar, starch, pectin, hemicellulose and cellulose from feedstuffs was developed to measure these carbohydrates in dietary and ruminal digesta samples. Recovery of dry matter (determined chemically) using this scheme was 60 to 70%. Data were obtained within the ranges of those in the literature for similar feedstuffs and(or) by similar methods. Dietary analysis by the sequential method yielded total recovery across all carbohydrate fractions of 87 and 81% for the high- and low-forage diets, respectively, and similar recoveries were obtained for the digesta samples. Analytical variation was small (≤ 15% CV), which permitted comparison of the carbohydrate profiles of the digesta over time. From these values, total ruminal digesta polysaccharide content was calculated and, when plotted over time, indicated that the disappearance per fraction corresponded with theoretical curves for ruminal fermentation of major feedstuff components. The postprandial variation within the bacterial population carbohydrate-fermenting groups was small, but changes were consistent with digesta component fermentation. Xylan- and cellulose-fermenting groups followed a pattern compatible with the disappearance of these polysaccharides from the rumen. In contrast, soluble sugar-fermenting groups predominated at all times despite the rapid rise and fall of these components in the digesta. Ruminal fluid pH, ammonia and total carbohydrate supported the digesta and bacterial trends observed. The data are interpreted to suggest that once daily maintenance feeding of high- or low- forage diets permits detection of digesta sugar and polysaccharide changes, supports a relatively stable microbial population while specific groups increase and decrease with the availability of substrate, and results in few differences in ruminal fluid traits.

Footnotes

1 The authors acknowledge F. B. Tesar for his assistance in preparing figures 2 and 3.

2 Microbiol, and Nutr. Res.

3 Dept. of Dairy Sci., present address of R. B. Hespell: Northern Reg Ctr., ARS-USDA, Peoria, IL 61604.






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Copyright © 1986 by the American Society of Animal Science.