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Influence of Energy and Protein Supplements on Grazing and Feedlot Performance of Steers¹

Colorado State University, Fort Collins 80523

Abstract

Two supplementation trials were conducted to evaluate the effect of (1) feeding energy during the spring grazing season, and protein during the fall and (2) the effect of supplementing energy during the entire summer grazing period. Also evaluated was the effect of supplements on subsequent feedlot performance.

Hereford steers grazing native range were fed supplemental feed containing .12 kg of digestible protein (DP) and 0, 1.24, 2.60, 3.96 and 5.32 Meal of metabolizable energy (ME) per day in individual stalls during a 32-day period in the spring. Steers from the spring treatments were alloted equally into groups fed 0, .14, .21, .28 and .36 kg of digestible protein during 30 days in the fall each year over a 3-year period. Steers in all treatments showed significantly greater gains (P<.05) than steers not receiving supplemental feed. The greatest response was obtained with the first increment of supplement during both periods. All steers receiving a protein supplement prior to entering the feedlot showed some improvement in performance during the finishing period. No interaction between spring and fall supplemental treatments existed, indicating that maximum returns can be expected when energy is fed in the spring and protein in the fall.

Steers fed 2.66 Meal of metabolizable energy during 63 days of grazing on annual rye also gained significantly more (P<.05) than non-supplemented steers and continuing to feed the energy for 70 additional days while grazing native range did not appreciably improve weight gains on grass. The results of these trials indicate that continuous energy supplementation during the grazing season will result in decreased feed-lot gain and efficiency, whereas protein supplementation during the latter part of the growing season enhances the performance of yearling cattle grazing native range and to a lesser extent, in the feedlot.

¹ Approved for publication as Scientific Paper 2188 of the Colorado Experiment Station. This study was conducted in cooperation with the Western Regional Research Project WRCC-8, formerly W-94, Range Livestock Nutrition.

² Associate Professor, Department of Animal Sciences, Colorado State University, Fort Collins, 80523, and Superintendent, San Juan Basin Research Center, Hesperus, CO. 81326.