Effect of Testosterone Propionate on Performance and Carcass Characteristics of Heifers and Cows

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Abstract
Two experiments were conducted to evaluate the effect of testosterone on growth and composition of cattle. In the first experiment, crossbred yearling heifers (n = 48) were assigned to four treatments: 1) control (no implant), 2) Synovex-H implants on d 1 and 84, 3) one testosterone propionate implant administered on d 1 and a second on d 84 and 4) two testosterone propionate implants administered on d 1. Heifers were fed a high-energy diet for the 157-d study. Implanting with the high-testosterone treatment improved (P < .05) daily gain and feed efficiency compared with the other treatments. Marbling score was reduced (P < .05) with the high-testosterone treatment. In Exp. 2, mature cows (n = 36) were assigned to one of three feeding periods (0, 42, or 84 d) with the cows fed 42 or 84 d subdivided into two groups (implanted with testosterone propionate or nonimplanted control). Cows were fed a high-energy diet and slaughtered at the end of each feeding period. Testosterone did not influence (P > .05) feedlot performance. Increased time on feed reduced (P < .01) daily gain (live weight basis) and feed efficiency but did not influence feed intake. Testosterone treatment had little influence on the fat and moisture contents of the carcass soft tissue or on the palatability characteristics of loin steaks. Time on feed increased lean muscle mass and carcass fat (P < .05). Sensory traits were improved at 42 d on feed (P < .05), but no further sensory improvement was observed at 84 d. In summary, testosterone propionate improved the performance of heifers but not of cows. Copyright © 1989. American Society of Animal Science . Copyright 1989 by American Society of Animal Science