Effect of Prenatal Androgenization on Lamb Performance, Carcass Composition and Reproductive Function

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Abstract
Two experiments were conducted in which pregnant crossbred ewes were randomly assigned to a control group or implanted with testosterone propionate/silastic implants between d 40 and d 60 of gestation. Implants contained approximately 2 g testosterone propionate and provided a constant delivery of 8.7 mg/d. Androgenized ewes (TE), born to implanted dams, had lower adjusted birth weights (P<.05) than control ewes (CE) in both experiments. Treated rams (TR) also displayed lower birth weights than control rams (CR) in both experiments, but the difference was significant only in Exp. 2. Average daily gain was 16.4% more (P<.05) for TE than for CE in Exp. 1. In Exp. 2, TE gained 9.6% faster (P<.05) and had 14.6% (P<.05) more weight per unit of feed consumed than CE. In both experiments, average daily gain and gain-to-feed ratio were similar for TR and CR. In Exp. 2, prenatal androgenization of ewes reduced (P<.05) 12th rib fat thickness and decreased (P<.05) percent kidney and pelvic fat. Yield grades of TE were lower than CE in both Exp. 1 (P<.10) and Exp. 2 (P<.05). From additional measurements taken in Exp. 2, liver weight per unit of carcass weight was greater (P<.05), anogenital distance was greater (P<.01) and test tube penetration into the vestibule was less (P<.01) for TE than CE. The TE did not exhibit regular estrous cycles, while CE displayed recurring estrous cycles. Copyright © 1987. American Society of Animal Science . Copyright 1987 by American Society of Animal Science