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Journal of Dairy Science Vol. 75 No. 2 520-532
© 1992 by American Dairy Science Association ®
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Influence of Rumen Fermentable Neutral Detergent Fiber Levels on Feed Intake and Milk Production of Dairy Cows

P. H. Robinson 1 and R. E. McQueen 1

1 Agriculture Canada Research Station, PO Box 20280, Fredericton, NB, Canada E38 427

Sixteen dairy cows in midlactation were fed four isonitrogenous (mean 2.46% N) mixed rations containing 46.4% DM and 40.7% NDF in a 16-wk Latin square design experiment. Diets were 42% barley-based concentrate, on a DM basis; forage was provided by combinations of two timothy silages of either slow (poor timothy) or rapid (good timothy) rumen fermentability and an alfalfa silage. Differences be tween the timothy forages caused the 24-h in sacco mixed diet NDF fementability, determined in dry cows fed hay, to be 53.8, 56.0, 60.2, and 62.1% in the four diets formulated to rise from 0% [as a percentage of total timothy DM] to 33, 66, and 100% good timothy. Intake of DM and NDF were not influenced by forage source. Rumen pool sizes of OM and NDF were similarly unaffected by treatment. Milk production increased linearly as the proportion of rapidly fermentable NDF in the diet increased, although the increases were small and not statistically significant, whereas BW gain declined (nonsignificantly). As a result, total net energy output was not influenced by diet. Although cows appeared able to extract more energy than expected from the slower fermenting forage, increasing levels in the diet resulted in a shift in energy output from milk products to BW gain, supported by a shift in rumen fermentation end products from propionic to acetic acid. Results do not appear to support the concept that NDF quality influences and can be used to predict voluntary feed intake. There is no indication that cows responded to more rapidly fermentable dietary NDF by increasing feed intake or extent of NDF fermentation in the rumen.

Key Words: fiber • intake • dairy cows

Submitted on August 7, 1991
Accepted on October 7, 1991




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L. O. Chow, V. S. Baron, R. Corbett, and M. Oba
Effects of Planting Date on Fiber Digestibility of Whole-Crop Barley and Productivity of Lactating Dairy Cows
J Dairy Sci, April 1, 2008; 91(4): 1534 - 1543.
[Abstract] [Full Text] [PDF]


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Copyright © 1992 by the American Dairy Science Association ®.