Journal of Animal Science, Vol 74, Issue 11 2860-2870, Copyright © 1996 by American Society of Animal Science

JOURNAL ARTICLE

Protein levels in beef cattle finishing diets: industry application, university research, and systems results

M. L. Galyean
Clayton Livestock Research Center, Department of Animal and Range Sciences, New Mexico State University 88415-9501, USA.

Consulting nutritionists were surveyed to determine current formulation and management practices for finishing beef cattle. Among the six consultants surveyed, percentage of CP in finishing diets ranged from 12.5 to 14.4%, with urea levels ranging from .5 to 1.5% of DM. Finishing diets were based primarily on highly processed, rapidly fermented grains (steam-flaked and high-moisture grain), with roughage levels ranging from 3 to 11% of DM. All six consultants considered feed bunk management to be a critical factor affecting feed intake and performance; five of the six consultants used aggressive implant programs based on estrogen + trenbolone acetate. Recent university research was reviewed with respect to CP level and source in finishing diets. Finishing cattle managed on aggressive implant programs seem to respond to higher levels of CP better than would be expected from the factorial calculation approach. Moreover, improvements in performance noted in recent research seemed to be more consistent when supplemental CP was derived from ruminally degraded vs undegraded sources. Calculation of protein requirements with a metabolizable protein (MP) system yielded estimates of protein needs by finishing cattle that agreed more closely with current industry practices than did calculation based on the factorial method. The difference between the MP system and the factorial method was primarily a result of accounting for microbial N needs in the MP system. Reasons for production responses to CP levels that are greater than those calculated by the factorial method include increased accretion of protein by rapidly growing, implanted cattle, particularly during the initial phase of the finishing period, alleviation of a microbial N deficiency, and ruminal and systemic effects of ruminally degraded N on acid-base balance of beef cattle fed rapidly fermented, high-grain diets. Reasons for production responses to supplemental CP need further research.

This article has been cited by other articles:

				J. T. Vasconcelos and M. L. Galyean Nutritional recommendations of feedlot consulting nutritionists: The 2007 Texas Tech University survey J Anim Sci, October 1, 2007; 85(10): 2772 - 2781. [Abstract] [Full Text] [PDF]

				W. Hu, M. R. Murphy, P. D. Constable, and E. Block Dietary Cation-Anion Difference and Dietary Protein Effects on Performance and Acid-Base Status of Dairy Cows in Early Lactation J Dairy Sci, July 1, 2007; 90(7): 3355 - 3366. [Abstract] [Full Text] [PDF]

				N. A. Cole, P. J. Defoor, M. L. Galyean, G. C. Duff, and J. F. Gleghorn Effects of phase-feeding of crude protein on performance, carcass characteristics, serum urea nitrogen concentrations, and manure nitrogen of finishing beef steers J Anim Sci, December 1, 2006; 84(12): 3421 - 3432. [Abstract] [Full Text] [PDF]

				D. K. Walker, E. C. Titgemeyer, J. S. Drouillard, E. R. Loe, B. E. Depenbusch, and A. S. Webb Effects of ractopamine and protein source on growth performance and carcass characteristics of feedlot heifers J Anim Sci, October 1, 2006; 84(10): 2795 - 2800. [Abstract] [Full Text] [PDF]

				S. L. Jaeger, M. K. Luebbe, C. N. Macken, G. E. Erickson, T. J. Klopfenstein, W. A. Fithian, and D. S. Jackson Influence of corn hybrid traits on digestibility and the efficiency of gain in feedlot cattle J Anim Sci, July 1, 2006; 84(7): 1790 - 1800. [Abstract] [Full Text] [PDF]

				N. A. Cole, L. W. Greene, F. T. McCollum, T. Montgomery, and K. McBride Influence of oscillating dietary crude protein concentration on performance, acid-base balance, and nitrogen excretion of steers J Anim Sci, November 1, 2003; 81(11): 2660 - 2668. [Abstract] [Full Text] [PDF]