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Effect of Synovex-S Implants and Kiln Dust on Tissue Gain by Feedlot Beef Steers

US Department of Agriculture, Beltsville, MD 20705

Abstract

Effects of Synovex-S implants and of a kiln dust (KD) diet on composition of tissue gain by Hereford steers were studied in a complete slaughter-balance trial. Four steers were slaughtered initially and four groups of six steers each were allowed ad libitum access to feed for 126 d in a factorial arrangement of treatments: unimplanted without or with KD in the diet, and implanted without or with KD in the diet. Initial full body weight averaged 310 kg and final full body weights of the unimplanted steers without and with KD and of implanted steers without and with KD were 454, 447, 497 and 498 kg, respectively. The respective final empty body weights were 415, 413, 463 and 457 kg. Steers implanted with Synovex-S consumed more feed dry matter (10.5 vs 9.3 kg/d), gained weight faster (1.35 vs 1.10 kg/d), and were more efficient (7.9 vs 8.7 kg feed dry matter/kg gain) than unimplanted steers. The KD diet did not affect performance. Carcass merit measurements were similar for steers in each treatment group. Steers implanted with Synovex-S retained 1.25 times more dry matter, 1.21 times more N, 3.00 times more ash, 1.23 times more ether extract and 1.24 times more energy than unimplanted steers. Implanted steers were 10% more efficient at converting feed gross energy to tissue gross energy but were not more efficient at converting feed nutrients to tissue protein. The KD diet did not significantly affect composition of gain, although there was a trend toward a synergistic effect of Synovex-S and the KD diet on ash and protein retention. Results showed that Synovex-S, like diethylstilbestrol, increases protein and ash retention in feedlot steers and that fat gain was increased by Synovex-S, probably as a result of greater feed intake by implanted steers.

¹ Ruminant Nutrition Laboratory, Animal Science Institute, ARS, USDA, Beltsville, MD 20705.

² The author acknowledges the efforts of Dr. W. E. Wheeler in experimental design, diet formulation and manuscript preparation, D. F. Hucht, A. S. Kozak, P. J. Rakowsky, E. D. Williams, and B. L. Phillips in sample preparation and Dr. B. W. Berry in carcass merit evaluation.