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University of Wisconsin4,5,, Madison 53706
Abstract
Four lactating Holstein cows fitted with T-type cannulae in the proximal duodenum were used in a 4 X 4 Latin square experiment to determine degradation in the rumen of protein in corn gluten meal. Cows were fed diets four times daily that contained 50% grain, 35% corn silage and 15% alfalfa hay on a dry matter (DM) basis. Corn gluten meal replaced low protein components of the grain mixture. Chromiumethylenediaminetetraacetic acid (Cr-EDTA) and La were included in portions of the grain mixtures to serve as indigestible markers for calculating nutrient flow rates and digestibilities. Grain mixtures were fed four times daily. Each experimental period was 14 d in duration and consisted of a 10-d adjustment period followed by a 4-d period for collection of feces and duodenal digesta. Mean ratios of Cr:La in the feed, duodenal digesta and feces were 5.62, 5.35 and 5.36, respectively. These results indicated that samples taken via the T-type cannula in the duodenum were reasonably representative of digesta flow past the cannula. Lanthanum was subsequently used as the sole digestibility marker for determining digesta flow rates. Apparent organic matter digestibility in the stomach averaged 41.5% and was about 30% higher when corrected for bacterial organic matter. Bacterial crude protein synthesis ranged from 15.7 to 17.7 g/100 g organic matter truly digested in the rumen. Regression of duodenal amino acid flow (y) on amino acid intake (x) indicated that 57 ± 11.1% of corn gluten meal protein left the rumen undegraded. Only 38 ± 10.8% of the lysine in corn gluten meal escaped degradation, and lysine was the most degradable of the amino acids.
1 Research supported by the College of Agr. and Life Sci., Univ. of Wisconsin, Madison, and by the Corn Refiners Assoc, Inc., Washington, DC.
2 Present address: Dept. of Anim. Sci., Univ. of Minnesota, St. Paul 55108.
3 Present address: Dept. of Vet. and Anim. Sci., Univ. of Massachusetts, Amherst 01003.
4 The authors gratefully acknowledge the technical assistance of Ms. Beth Jones, Ms. Vicky Voss and Mr. Paul Fritschel. The assistance of Dr. Lon Whitlow in cannulation of the cows is also acknowledged. The authors also wish to thank Dr. Arden Hardie for help with the statistical analysis and Mr. Ralph Lance for care of the animals.
5 Dept. of Daity Sci. and Dept Vet. Sci.
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