Thirty-one Hampshire Down, Ile de France and Suffolk crossbred lambs divided into four treatments: intact, castrated with burdizzo, with rubber bands and with knife, were used in this experiment. Castration occurred at 58 days of age. After weaning, at 84 days, the animals were fed lot until 30 to 32 kg of live weight, and then slaughtered. There were no significant differences among treatments and genetic groups for birth, weaning and slaughter weights, for average daily gain from birth to slaughter, and for age at slaughter. The average daily weight gain from birth to slaughter were 0.179, 0.177, 0.170 and 0.147 kg, and the age at slaughter were 152.2, 156.0, 161.5 and 188.9 days, respectively, for intact, castrated with burdizzo, with rubber bands and with knife lambs. Hampshire Down, Ile de France and Suffolk had 0.176; 0.163 and 0.166 kg of average daily weight gain, respectively. Intact lambs presented lower carcass true yields; there were no other important differences among treatments for the studied traits. Hampshire Down lambs presented greater cold carcass yields, while Suffolk had lower carcass true yields and lower neck percentage, and the Ile de France showed the shortest carcasses. Birth weight had significant effects on lamb weight gains and age at slaughter. The results suggest no significant differences on the performance of intact and castrated by different methods lambs slaughtered between 30 to 32 kg, and that meat lambs from different genetic groups can present significant differences when slaughter at same weight.
age at slaughter; carcass; genetic group; sheep; weight gain
