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A simulation study of open nucleus and closed nucleus breeding systems in a sheep population

Published online by Cambridge University Press:  02 September 2010

J. A. Roden
J. A. Roden
Affiliation:
Department of Agriculture, University of Aberdeen, 581 King Street, Aberdeen AB9 1UD
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Abstract

Stochastic simulation was used to compare the results of alternative breeding systems in a sheep population divided into 10 flocks of 120 ewes. The breeding systems compared were selection within closed flocks (CF), a closed nucleus system (CNS), an open nucleus system (ONS) and open nucleus systems with the selection of nucleus replacements being restricted to either nucleus born males (ONSRm) or nucleus born females (ONSRf). Selection was for a best linear unbiased prediction of breeding value for lamb live weight which had a heritability of 0·17. The open nucleus breeding systems (ONS, ONSRm, ONSRf) resulted in higher rates of genetic gain, more predictable selection responses and lower rates of inbreeding than either the closed nucleus system (CNS) or selection within closed flocks (CF). Initial genetic differences between flocks resulted in higher rates of genetic gain in the nucleus breeding systems due to the use of between flock genetic variance. In the ONS system up to 25% of nucleus sires and approximately 50% of nucleus dams were born in base flocks. Nevertheless if selection of either nucleus sires or dams was restricted to nucleus born animals there was very little change in genetic gain or rate of inbreeding.

Keywords

breeding programmessheepsimulation models
Type
Research Article
Information
Animal Science , Volume 60 , Issue 1 , February 1995 , pp. 117 - 124
Copyright
Copyright © British Society of Animal Science 1995

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