Effect of Type of Protein Supplementation on Duodenal Amino Acid Flow and Absorption in Lactating Dairy Cows

¹ Department of Animal Science Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot 76100, Israel
² Institute of Animal Science, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel

Four multiparous lactating Holstein cows, fitted with cannulas in the rumen, duodenum, and ileum, were used in a trial with a 4 x 4 Latin square design to examine the effect of source and degradability of dietary CP supplements on AA flow and absorption in the small intestine. The CP supplements consisted of fish meal or meat meal as the animal by-products supplement and soybean meal or heated soybean meal as the plant by-products supplement. Fish meal and heated soybean meal constituted the high RUP diets, and meat meal and soybean meal constituted the low RUP diets.

Dry matter intakes were similar among treatments. However, intakes of OM, rumen-degradable OM, total CP, and RDP were affected by the source of the CP supplement and were higher for diets with plant by-products than for those diets with animal by-products. Data were similar for the calculated in situ digestibilities and for true in vivo digestibilities of rumen-degradable OM. Efficiency of bacterial CP synthesis was similar among diets; however, nonbacterial CP flow to the duodenum and OM, CP, and disappearance of AA from the small intestine were affected by the interaction of supplement source and degradability. Heat treatment of soybean meal reduced the availability of most of the essential AA for absorption in the small intestine by 2.3% compared with that of soybean meal; the biggest such reduction (20%) occurred for Met.

Availability of AA in the small intestine was affected by source and degradability of the CP dietary supplement. Heat treatment at 140°C for 2.5 h reduced the availability of Met absorption from the small intestine. Although the differences among availabilities of the individual AA in the small intestine ranged from 80 to 84% among treatments, for high yielding cows, these differences may have practical significance.

Key Words: protein supplementation • amino acid • flow • duodenum • lactating cows

Submitted on June 8, 1995
Accepted on March 22, 1996

This article has been cited by other articles:

				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]

				I. R. Ipharraguerre, J. H. Clark, and D. E. Freeman Rumen Fermentation and Intestinal Supply of Nutrients in Dairy Cows Fed Rumen-Protected Soy Products J Dairy Sci, August 1, 2005; 88(8): 2879 - 2892. [Abstract] [Full Text] [PDF]

				H. G. Bateman II, J. H. Clark, and M. R. Murphy Development of a System to Predict Feed Protein Flow to the Small Intestine of Cattle J Dairy Sci, January 1, 2005; 88(1): 282 - 295. [Abstract] [Full Text] [PDF]

				W. Z. Yang and K. A. Beauchemin Grain Processing, Forage-to-Concentrate Ratio, and Forage Length Effects on Ruminal Nitrogen Degradation and Flows of Amino Acids to the Duodenum J Dairy Sci, August 1, 2004; 87(8): 2578 - 2590. [Abstract] [Full Text] [PDF]