Influence of Dietary Protein Sources on the Amino Acid Profiles Available for Digestion and Metabolism in Lactating Cows

¹ Department of Animal Sciences, University of Arizona, Tucson 85721 and Department of Animal Science, Michigan State University, East Lansing 48824

Six lactating Holstein cows, fitted with T-type cannulas in the proximal duodenum, were used in a replicated 3 x 3 Latin square design to determine influence of supplemental protein on amino acid profiles of duodenal chyme and plasma. Protein sources were blood meal, corn gluten meal, and cottonseed meal, which furnished approximately 46% of the total protein in corn-grain corn silage diets. Markers were ¹⁵N to estimate rumen bacteria and chromic oxide to estimate nutrient flow. Dry matter intake was lowest on blood meal. Duodenal flow of N exceeded N intake 23% on blood meal and corn gluten meal. Percentages of organic matter and protein digested in the rumen were 56.5, 41.8; 61.2, 53.4; and 50.6, 56.2 for the respective diets. Variation in patterns of amino acids flowing to the duodenum, but not in coccygeal blood, closely reflected dietary differences with six of eight essential amino acids highest for the same treatment in both diet and duodenal chyme. Essential amino acids in least abundance for milk production, measured by mammary extraction coefficients, differed among diets. We conclude that supplemental protein source influences greatly the quantity and pattern of amino acids available for digestion in lactating dairy cows.

Key Words: lactating cow • amino acids • protein sources

Submitted on December 11, 1989
Accepted on April 11, 1990

This article has been cited by other articles:

				A. F. Brito, G. F. Tremblay, A. Bertrand, Y. Castonguay, G. Belanger, R. Michaud, H. Lapierre, C. Benchaar, H. V. Petit, D. R. Ouellet, et al. Alfalfa Cut at Sundown and Harvested as Baleage Improves Milk Yield of Late-Lactation Dairy Cows J Dairy Sci, October 1, 2008; 91(10): 3968 - 3982. [Abstract] [Full Text] [PDF]

				J. C. Marini, D. G. Fox, and M. R. Murphy Nitrogen transactions along the gastrointestinal tract of cattle: A meta-analytical approach J Anim Sci, March 1, 2008; 86(3): 660 - 679. [Abstract] [Full Text] [PDF]

				A. F. Brito and G. A. Broderick Effects of Different Protein Supplements on Milk Production and Nutrient Utilization in Lactating Dairy Cows J Dairy Sci, April 1, 2007; 90(4): 1816 - 1827. [Abstract] [Full Text] [PDF]

				A. F. Brito, G. A. Broderick, and S. M. Reynal Effect of varying dietary ratios of alfalfa silage to corn silage on omasal flow and microbial protein synthesis in dairy cows. J Dairy Sci, October 1, 2006; 89(10): 3939 - 3953. [Abstract] [Full Text] [PDF]

				I. R. Ipharraguerre and J. H. Clark Impacts of the Source and Amount of Crude Protein on the Intestinal Supply of Nitrogen Fractions and Performance of Dairy Cows J Dairy Sci, May 1, 2005; 88(e_suppl_1): E22 - E37. [Abstract] [Full Text] [PDF]