<h2> Effects of method and age at castration on growth rate and meat quality of bulls</h2> <h3> T. W. KNIGHT G. P. COSGROVE M. G. LAMBERT A. F. DEATH</h3> <h4> AgResearch Grasslands Private Bag 11008 Palmerston North, New Zealand</h4> Abstract Post-pubertal castration of bulls may combine the faster growth rate and more efficient feed conversion of bulls with the meat quality of steers. In Experiment 1, the effects of method of castration at 17 months of age (surgical castration versus immunocastration) on LWG and carcass characteristics were compared for bulls, bulls castrated post-puberty (castrates), and bulls castrated pre-puberty (steers). Bulls were 20 kg heavier (P < 0.001) than steers at castration at 17 months of age, but over the 101-day finishing period, castrates grew slower than steers (0.67 versus 0.83 kg per head d-1) and both groups grew slower than bulls (0.99 kg per head d-1; P < 0.05). As a result of this lower LWG after castration, carcass weight was similar for castrates and steers, and both groups were lighter than bulls. Experiment 2 was conducted to test whether the prolonged depression in LWG following castration was related to the age at castration, and for comparison with the LWG of steers treated with Compudosereg.. Bulls were castrated surgically at 12, 15, and 17 months of age. Lower LWG for the three groups of castrates resulted in similar carcass weights for castrates and steers. For both experiments, post-pubertal castration resulted in carcasses with steer-like characteristics, although the rate of change depended on the attribute being measured and the age at castration. Keywords cattle; castration; growth; carcass characteristics; meat quality New Zealand Journal of Agricultural Research, 1999, Vol. 42: 255-268 0028-8233/99/4203-0255 $7.00/0 (c) The Royal Society of New Zealand 1999 Knight et al.--Castration effects on growth rate and meat quality

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