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Responses to selection for pubertal traits in Angus cattle over 23 years
Amyes NC, Morris CA
Proceedings of the New Zealand Society of Animal Production, Volume 69, pp 201-205, Jun 2009
Proceedings of the New Zealand Society of Animal Production, Volume 69, pp 201-205, Jun 2009
Article class: Conference Presentation
Subject Terms: Breed/breeding, Genetics, Growth/development, Puberty, Reproduction
Animal Type: Cattle
Publisher: New Zealand Society of Animal ProductionAbstract
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 ± 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 ± 0.03 (standardised AFO), and 0.40 ± 0.04 (individual SC records; repeatability over ages, 0.68 ± 0.01). Averaging over recent year'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.The whole of the literary matter of the Proceedings of the New Zealand Society of Animal Production is copyright New Zealand Society of Animal Production, Downloading this article signifies agreement with the terms and conditions of electronic access.
