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Journal of Dairy Science Vol. 84 No. 12 2721-2729
© 2001 by American Dairy Science Association ®
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Rumen Acid Production from Dairy Feeds. 1. Effects on Feed Intake and Milk Production of Dairy Cows Offered Grass or Corn Silages

R. J. Dewhurst 1, D. Wadhwa 2, L. P. Borgida 3, and W. J. Fisher 4

1 Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, SY23 3EB, UK
2 Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, SY23 3EB, UK and Institute of Rural Studies, University of Wales, Aberystwyth, Ceredigion, SY23 3AL, UK
3 COFNA, 25 Rue du Rempart, Tours, Cedex, France
4 Institute of Grassland and Environmental Research, Trawsgoed, Aberystwyth, SY23 4LL, UK

Earlier studies developed a new approach to feed evaluation, measuring the net acid load that develops during rumen fermentation. Two concentrates were formulated to be isoenergetic and isonitrogenous, with extremes of rumen acid load. A third treatment comprised a 50:50 mixture of these concentrates. These concentrates were evaluated along with ryegrass silage and corn silage. The feeds were evaluated in a continuous culture system adapted to deliver and record the quantities of acid or alkali needed to maintain a constant pH (6.2 to 6.3). This study confirmed the anticipated ranking of concentrates for rumen acid load, as well as the highly acidogenic nature of corn silage. The concentrates were formulated to balance corn silage and were offered to early-lactation Holstein-Friesian cows at 50% of dry matter intake, with either ryegrass silage or corn silage. Feed intake was lower for animals offered corn silage-based diets (17.4 vs. 22.2 kg of dry matter/d). Increasing concentrate acid load led to a large decline in dry matter intake for corn silage, although not for grass silage. Feed intake effects were reflected in significant effects on yield of milk (31.0, 29.9, and 26.9 kg/ d for low-, medium-, and high-acid load concentrates, respectively) and milk solids. Milk protein concentration was unaffected by concentrate type with corn silage diets but tended to be higher when high acid load concentrates were fed with grass silage. This may reflect the effect of the high starch concentrate rectifying a shortage of glucogenic precursors or microbial protein with the grass silage-based diet.

Key Words: concentrates • rumen pH • milk production • silages

Submitted on March 19, 2001
Accepted on August 3, 2001




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B. Rustomo, O. AlZahal, N. E. Odongo, T. F. Duffield, and B. W. McBride
Effects of Rumen Acid Load from Feed and Forage Particle Size on Ruminal pH and Dry Matter Intake in the Lactating Dairy Cow
J Dairy Sci, December 1, 2006; 89(12): 4758 - 4768.
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