J. Anim Sci.
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J. Anim Sci. 1986. 62:509-520.
© 1986 American Society of Animal Science
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The Influence of Diet and Protozoal Numbers on the Breakdown and Synthesis of Protein in the Rumen of Sheep1

J.H.F. Meyer2, S. I. van der Walt2 and H. M. Schwartz2

National Chemical Research Laboratory, Pretoria, Republic of South Africa, 0001

Abstract

Four sheep with a rumen fistula and re-entrant duodenal cannulae were sequentially fed three diets containing corn stover, fishmeal, molasses and 0, 30 and 61% ground corn respectively. Protozoal numbers, rumen volume and outflow rate of liquids and solids, as well as flow of organic matter (OM) and N to the duodenum, were measured twice in each sheep on each diet. Two sheep were fed the 30% corn diet, defaunated and measurements repeated. Protozoal numbers increased with the grain content of diet. The protozoal N pool in the rumen was 1.4, 4.9 and 7.1 g for diets containing 0, 30 and 61% corn. The flow of non-ammonia N (NAN) and amino acid N to the duodenum increased with the amount of grain fed. The essential amino acids at the duodenum were 92, 114 and 140% of intake for diets containing 0, 30 and 61% corn respectively. The flow of total microbial NAN (measured with 3S S as a marker) and bacterial NAN (measured with diamino-pimelic acid) were not influenced by diet, but were increased (P<.05) by defaunation. Protozoal NAN, obtained by difference, constituted on the average 38% of the total microbial NAN reaching the duodenum of faunated sheep. The energetic efficiency of microbial NAN synthesis was 27 g per kg OM apparently digested in the rumen on all diets. It was increased (P<.05) to 43 g by defaunation. In faunated sheep there was no correlation between number or volume of protozoa in the rumen and efficiency of microbial protein synthesis there. Flow of feed and endogenous NAN to the duodenum was higher (P<.001) on the 30% and 61% corn-containing diets. The rumen degradation of N in diets containing 0, 30 and 61% corn was estimated to be 94, 78 and 77% in vivo and 71, 76 and 73% in sacco.

Footnotes

1 The authors are indebted to: The Director of the Vet. Res. Inst, for facilities for carrying out this work at Onderstepoort; the late Mr. B. Briel for cannulating the sheep, and Mr. S. Nkosi for their care; Dr. F.M.C. Gilchrist for advice and assistance in counting the protozoa; Dr. J. Dijkstra for the amino acid analyses; Dr. C. Z. Roux for help with the statistical analyses and Mr. P. Wood for technical assistance.

2 Present address: Lab. for Molecular and Cell Biol., Anaerobic Microbiol. Division, Private Bag X3, Onderstepoort, 0110, Republic of South Africa.






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Copyright © 1986 by the American Society of Animal Science.