@conference {60976,
	title = {Responses to selection for pubertal traits in Angus cattle over 23 years},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {69},
	year = {2009},
	month = {Jun},
	pages = {201-205},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Selection to change age at puberty over 23 years was monitored in Angus cattle in a Ruakura study. A foundation herd was divided in 1984 into four lines: a control unselected line, and lines selected for high age-at-puberty (Age+), low age-at-puberty (Age-), and high scrotal circumference (SC), with the last two lines being merged later. Age at puberty (first oestrus, AFO) was determined in heifers from observations of first behavioural oestrus date; puberty was determined in bulls from SC records from 8 to 13 months of age. Selection for AFO was applied mainly to bulls, using the genetic correlation between AFO and SC from our data (-0.25 {\textpm} 0.09). Puberty records from 6,473 weaned calves were analysed, using restricted maximum likelihood methods to determine genetic changes achieved by line. Realised heritability estimates were 0.26 {\textpm} 0.03 (standardised AFO), and 0.40 {\textpm} 0.04 (individual SC records; repeatability over ages, 0.68 {\textpm} 0.01). Averaging over recent year{\textquoteright}s data, Age- line heifers had lower AFO than Age+ line heifers by 69 days (19\%; 1.33 phenotypic standard deviations), and bulls had larger SC by 3.0 cm (9.9\%; 1.17 phenotypic standard deviations). Correlated responses in pregnancy rate favoured Age- over Age+ females at all ages. },
	issn = {1176-5283},
	author = {Amyes NC and Morris CA}
}
