Altering the influence of the testicles of male lambs is used to manipulate growth and body composition. To determine the effects on carcass weight and consequently returns to farmers, an analysis was undertaken from studies in the scientific literature in which animals were slaughtered at the same time. Each dataset was treated as if it were a random event and a model of sex type (including ram, cryptorchid, and wether) was fitted. Rams, cryptorchids and wethers slaughtered on the same date had similar carcass weights. Cryptorchid carcass weights ranged from 95Á102%, and wethers 87Á107%, of the weight of ram carcasses. Based on this range in responses to altering testicular function, at an intermediate carcass weight of 17.5 kg and at $4/kg, returns from cryptorchids ranged from $3.50 less than to $1.40 more than rams. Similarly, returns from wethers ranged from $9.10 less than to $4.90 more than rams. In conclusion, the carcass weight benefits of not castrating ram lambs are variable and, depending on lamb prices, the financial gains will be small when slaughtered at the same age. However, these results need to be interpreted in light of other animal husbandry and animal welfare requirements and expectations.

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