Effect of Degradability of Dietary Protein and Fat on Ruminal, Blood, and Milk Components of Jersey and Holstein Cows

¹ Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061-0315

Twelve Holstein cows and 12 Jersey cows were used in six 4 x 4 Latin squares to investigate the effects of the degradability of dietary protein and supplemental dietary fat on milk components. Dietary dry matter contained 16% crude protein with two concentrations of ruminally undegradable protein (RUP) obtained by substituting blood meal for a portion of the soybean meal. Treatments were 1) 29% RUP, 0% added fat; 2) 29% RUP, 2.7% added fat (Ca soaps of fatty acids); 3) 41% RUP, 0% added fat; and 4) 41% RUP, 2.7% added fat. The dry matter of the total mixed ration fed at 1000 and 1400 h consisted of 30% corn silage, 29% alfalfa haylage, and 41% concentrate. Supplemental dietary fat depressed dry matter intake by 6.2%. Plasma urea N was greater at 0700 and 1600 h for Jerseys fed diets containing added fat and greater at 0700 h for Holsteins fed diets containing 41% RUP than for Holsteins fed 0% added fat and 29% RUP. When averaged across both breeds, milk production increased 7.1%, and production of 4% fat-corrected milk by Jerseys increased 8.4%, in response to added dietary fat. Milk protein was reduced when Holstein diets contained 41% RUP. Milk protein content was reduced 7.1 and 3.9%, and milk urea N was increased 4.9 and 8.5%, by added fat and 41% RUP in both breeds, respectively. Added fat reduced the concentration, but not the yield, of milk components. Substitution of blood meal decreased the concentration and yield of milk protein and casein N.

Key Words: protein • fat • milk components milk ureanitrogen)

Submitted on November 6, 1995
Accepted on May 10, 1996

This article has been cited by other articles:

				P. C. Aikman, C. K. Reynolds, and D. E. Beever Diet Digestibility, Rate of Passage, and Eating and Rumination Behavior of Jersey and Holstein Cows J Dairy Sci, March 1, 2008; 91(3): 1103 - 1114. [Abstract] [Full Text] [PDF]

				H. M. Hammon, C. C. Metges, P. Junghans, F. Becker, O. Bellmann, F. Schneider, G. Nurnberg, P. Dubreuil, and H. Lapierre Metabolic Changes and Net Portal Flux in Dairy Cows Fed a Ration Containing Rumen-Protected Fat as Compared to a Control Diet J Dairy Sci, January 1, 2008; 91(1): 208 - 217. [Abstract] [Full Text] [PDF]

				A. R. J. Cabrita, R. J. B. Bessa, S. P. Alves, R. J. Dewhurst, and A. J. M. Fonseca Effects of Dietary Protein and Starch on Intake, Milk Production, and Milk Fatty Acid Profiles of Dairy Cows Fed Corn Silage-Based Diets J Dairy Sci, March 1, 2007; 90(3): 1429 - 1439. [Abstract] [Full Text] [PDF]

				M. A. Wattiaux, E. V. Nordheim, and P. Crump Statistical Evaluation of Factors and Interactions Affecting Dairy Herd Improvement Milk Urea Nitrogen in Commercial Midwest Dairy Herds J Dairy Sci, August 1, 2005; 88(8): 3020 - 3035. [Abstract] [Full Text] [PDF]

				K. W. Bailey, C. M. Jones, and A. J. Heinrichs Economic Returns to Holstein and Jersey Herds Under Multiple Component Pricing J Dairy Sci, June 1, 2005; 88(6): 2269 - 2280. [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]

				D. Hojman, M. Gips, and E. Ezra Association Between Live Body Weight and Milk Urea Concentration in Holstein Cows J Dairy Sci, February 1, 2005; 88(2): 580 - 584. [Abstract] [Full Text] [PDF]

				D. Hojman, O. Kroll, G. Adin, M. Gips, B. Hanochi, and E. Ezra Relationships Between Milk Urea and Production, Nutrition, and Fertility Traits in Israeli Dairy Herds J Dairy Sci, April 1, 2004; 87(4): 1001 - 1011. [Abstract] [Full Text] [PDF]

				A. Arieli, G. Adin, and I. Bruckental The Effect of Protein Intake on Performance of Cows in Hot Environmental Temperatures J Dairy Sci, March 1, 2004; 87(3): 620 - 629. [Abstract] [Full Text] [PDF]