Genotype selection for superior growth and muscling advances the onset of puberty in merino ewes

The present study evaluated the impact of selection for high muscle and high growth on puberty. One hundred and thirty six Merino ewe lambs with Australian Sheep Breeding Values (ASBVs) at post-weaning age for liveweight (PWT) and depth of eye muscle (PEMD) and fat (PFAT) were used. Analyses were completed to determine how these production traits were related with the onset of puberty during the teasing period. Overall, 89% of lambs reached puberty when lambs weighed (±SEM) 40 ± 0.5 kg and were 222 ± 3.5 days old (179-248 days) at their first oestrus. Puberty was accelerated by PWT, PEMD and PFAT, but the effects of PEMD and PFAT were due to correlated changes in PWT. We concluded that genetic selection for high growth will accelerate the onset of puberty in Merino ewes