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Effects of Rumen-Protected Methionine and Lysine on Ruminant Performance and Nutrient Metabolism^1,2,

The Ohio State University^,6, Wooster 44691 and Eastman Chemicals Division Research Laboratories, Rochester, NY 14603

Abstract

Four trials were conducted to determine the effects of supplemental rumen-protected methionine (RPMet) and lysine (RPLys) on lamb N metabolism and steer feedlot performance. In trial 1, 20 Suffolk-sired, crossbred lambs (avg weight 32 kg) were fed diets containing no supplemental methionine (Met) and lysine (Lys), .03% RPMet, .05% RPLys or .03% RPMet + .05% RPLys. Lambs fed .03% RPMet + .05% RPLys had a 33% increase in N retention compared with lambs fed no supplemental Met and Lys. In trial 2, to verify the protection and availability of these amino acids, five Targhee lambs (avg weight 35 kg) were fed corn-soybran flake diets supplemented with urea and were assigned in a 5 x 5 Latin square to one of the following treatments: 1) control; 2) .03% RPMet + .05% RPLys offered in the diet; 3) .03% RPMet + .05% RPLys abomassally infused; 4) .03% non-protected Met + .05% non-protected Lys offered in the diet and 5) .03% Met + .05% Lys abomasally infused. Treatments 2, 3 and 5 decreased (P<.05) urinary N (g/d) and increased N retention (P<.05) compared with the control diet (treatment 1). Increases (P<.05) in plasma Met and Lys concentrations indicated that the amino acids were protected and available for animals at the site of absorption. In trial 3, 40 crossbred Angus steers (avg weight 247 kg) were fed diets composed of 53% corn silage and 47% concentrate and supplemented with soybean meal to 11.3% crude protein. Steers that were fed diets containing .19% RPMet + .11% RPLys had greater daily gain (P<.05) than those fed diets containing no supplemental amino acids, .11% RPMet + .01% RPLys, and .15% RPMet + .06% RPLys (1.39 vs 1.23, 1.22 and 1.20 kg/d, respectively). Similar improvements in feed conversion resulted and increases in plasma Met concentrations followed the same trend. In trial 4, 40 crossbred Angus steers (avg weight 368 kg) were fed corn grain-corn silage diets supplemented with urea. Treatments were: no supplemental amino acids; .05% RPMet + .01% RPLys; .10% RPMet + .04% RPLys; and .15% RPMet + .07% RPLys. No differences in steer performance resulted due to supplemental RPMet and RPLys (P>.05). The results of these trials suggest that the RPMet and RPLys used in this study are protected from ruminal degradation, are available post-ruminally and can improve lamb N balance and growing steer performance.

¹ Salaries and research support provided by State and Federal Funds appropriated to the Ohio Agr. Res. and Dev. Center, The Ohio State Univ., Journal Article No. 91-85.

² Partial research support and rumen-protected amino acids provided by Eastman Chemicals Division, Rochester, NY 14603.

³ Dept. of Anim. Sci.

⁴ Reprint requests: Dept. of Anim. Sci., Ohio Agr. Res. and Dev. Center, Wooster, OH 44691.

⁵ Health and Nutr. Res. Division, Eastman Chemicals Division, P.O. Box 1911.

⁶ Ohio Agr. Res. and Dev. Center.