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Luteinizing Hormone, Testosterone, Growth and Carcass Reponses to Sexual Alteration in the Ram¹

U. S. Department of Agriculture^,3, Clay Center, Nebraska 68933

Abstract

A total of 130 ram lambs were used in a study to determine the effects of sex alteration on serum hormone levels, growth rate and carcass traits. Sex alteration included no treatment (intact rams), scrotal ablation to alter normal testicular secretion (short scrotum rams) and castration to completely remove influences derived from the testes (wethers). Although these data suggest that scrotal ablation at birth did not produce complete azoospermia in Finn-crossbred rams, reduction (P<.01) in testicular weight did produce significant results. Serum testosterone in short scrotum and intact rams was similar, whereas castration resulted in considerably lower concentrations of this steroid (P<.01). On the other hand, serum luteinizing hormone was increased (P<.01) threefold in short scrotum rams and 12-fold in wethers as compared to that of intact rams. Because these results cannot be fully explained by changes in serum testosterone, it is speculated that changes in secretory products of the testis which accompany degeneration of the germinal epithelium are responsible for elevated luteinizing hormone

Post-weaning average daily gain (P<.01) and feed efficiency were highest in intact and short scrotum rams indicating that testosterone (or testis) may be beneficial. Although dressing percentage and adjusted backfat were highest (P<.01) in wethers, carcass weight and yield grade were advantageous (P<.01) in short scrotum and intact rams. Quality grades were similar; all animals reached average choice.

¹ The authors gratefully acknowledge Ms. Marti Brown and Ann Hultine for their laboratory assistance and Mr. Brad Knapp for helping with the statistical analyses. Cooperation of the Nebraska Agricultural Experiment Station, University of Nebraska, Lincoln, is acknowledged.

² U. S. Meat Animal Research Center, Agricultural Research Service.

³ Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable.