Reduction of testicular parenchyma at marking: effect on lamb growth, carcass fatness and sexual development

Abstract

Growth and carcass parameters were studied for 296 lambs comprising 141 males and 155 ewes. The males were either castrated (wethers) or vasectomised and hemicastrated with the parenchyma of the retained testicle reduced (cryptorchids), or they had the parenchyma of both testicles reduced (rams). Wether and ram lambs grew at a similar rate, the latter group growing significantly (P<0.05) faster to first slaughter than cryptorchid and ewe lambs. Ewe lambs grew significantly (P<0.05) slower than those from the other groups. Ewe lambs were significantly (P<0.05) fatter at slaughter than lambs in all other groups, and wether lambs were fatter (P<0.05) than the cryptorchid and ram lambs. Sexual competency of the cryptorchid and ram lambs was assessed by testicle examination, which showed that the cryptorchid lambs were not likely to produce viable sperm. In contrast, there was evidence that the treatment applied to the ram lambs would not prevent production of viable sperm, and they had the potential to sire lambs. This fertility was attributed to the retention of the scrotal sac. The technique used for the cryptorchid lambs involving scrotal ablation was deemed to offer the most potential in terms of lean tissue growth tempered against sexual competency and development of undesirable male characteristics.