GROWTH AND BODY COMPOSITION OF ENTIRE AND CASTRATED FALLOW BUCKS (DAMA DAMA) TREATED WITH ZERANOL

摘要

A 2 X 2 factorial experimental design was used to compare growth in entire and castrated fallow bucks, implanted with zeranol at 6 and 9 months of age, or left as controls (no. = 10 per group). Growth pattern at pasture was assessed using 10-monthly growth periods from weaning (6 months) to 17 months. There were no overall castration or zeranol effects on growth rates from weaning to 17 months (P > 0.05), although there were significant interactions of zeranol and castration with time (P < 0.05). Zeranol-treated animals grew faster than the controls from 6 to 14 months, compared with the last 3 months (P < 0.05), indicating that the zeranol implants given at 6 and 9 months of age were no longer effective over the last 3 months of the experiment. The interaction between castration and time was significant (P < 0.05), whereby entire males grew relatively faster than the castrated males in both spring and the average of the winter and spring periods, whilst there was little difference in growth rates between entire and castrated males during the autumn period.