The timing of the commencement of the breeding season in Boer and rangeland goats raised in the tropics of Queensland, Australia

- There is a difference in the onset of the breeding season between breeds of goats.
- Boer goats started the breeding season two months earlier than rangeland goats.
- There are differences in sensitivity to photoperiod between these breeds.
- Boer goats may be a better option than rangeland goats.

This study aimed to determine the timing of the onset of the breeding season in Boer and rangeland goats raised in a tropical region of northern Queensland. The experiment was carried out using 25 Boer and 20 rangeland female goats. Boer and rangeland goats were kept on the same pasture in the absence of males and supplemented to provide nutritional requirements above maintenance. Blood samples were collected once weekly from December 2011 to May 2012 and analyzed for concentrations of progesterone. The mean time to first ovulation was found to occur earlier in Boer compared to rangeland goats (64.7 ± 5.0 days vs. 87.7 ± 5.6 days, respectively; P < 0.05). Differences in survival curves (P < 0.05) for the timing of onset of first ovulation between breeds were also detected. Boer goats started ovulating in December (8.3%) and had all ovulated by March while most rangeland goats started ovulating in March (84%) and had all ovulated by the end of April. These results demonstrate that in a tropical region of north Queensland Boer goats commence ovulatory cycles earlier than rangeland goats which may be beneficial if an earlier start to the breeding season is preferred.