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Three-tier open nucleus breeding schemes

Published online by Cambridge University Press:  02 September 2010

R. K. Shepherd
R. K. Shepherd
Affiliation:
Department of Mathematics and Computing, Central Queensland University, Rockhampton, Queensland 4702, Australia
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Abstract

Optimum designs of three-tier open nucleus breeding schemes are evaluated deterministically by maximizing the equilibrium rate of genetic gain for two methods of selection. Methodology is developed for both restricted and unrestricted migration between tiers and incorporates the loss of variance due to selection. A formula is derived for calculating the asymptotic rate of inbreeding. In the extensive livestock industries, proportional improvements in the equilibrium rate of genetic gain of between 0·12 and 0·22 are possible over a closed nucleus if no restrictions are imposed on male and female migration between tiers. The value of the extra tier in an optimized three-tier open nucleus scheme is approximately 0-45 of the maximum proportional improvement of a two-tier open nucleus over a closed nucleus scheme. The optimum structure is to have approximately 1% and 10% of the population in the nucleus and multiplier respectively. With this optimum structure the asymptotic rate of inbreeding will be reduced to one-sixth of that in a closed nucleus. The effects of various factors on the optimum structure, genetic gain and inbreeding are examined. The advantage of a three-tier open nucleus scheme over a closed nucleus scheme can be reduced substantially if thesefactors are operating.

Keywords

best linear unbiased predictionbreeding programmesinbreedingselection
Type
Research Article
Information
Animal Science , Volume 65 , Issue 3 , December 1997 , pp. 321 - 334
Copyright
Copyright © British Society of Animal Science 1997

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References

Atkins, K. D. 1987. Potential responses to selection in Merino sheep given current industry structure and selection practices. In Merino inprovement programs in Australia (ed. McGuirk, B. J.), pp. 299–312. Australian Wool Corporation, Melbourne.Google Scholar
Bichard, M. 1971. Dissemination of genetic improvement through a livestock industry. Animal Production 13: 401–411.Google Scholar
Carrick, M. and England, D. P. 1990. The Merinotech structure and across-flock breeding value prediction. Proceedings of the Australian Society of Animal Production 8: 223–226.Google Scholar
Dekkers, J. C. M. 1992. Asymptotic response to selection on best linear unbiased predictors of breeding values. Animal Production 54: 351–360.Google Scholar
Hill, W. G. 1974. Prediction and evaluation of response to selection with overlapping generations. Animal Production 18:117–140.Google Scholar
Hopkins, I. R. 1978. Some optimu m age structures and selection methods in open nucleus breeding schemes with overlapping generations. Animal Production 26: 267–276.Google Scholar
Hopkins, I. R. and James, J. W. 1978. Theory of open nucleus breeding systems with overlapping generations. Theoretical and Applied Genetics 53:17–24.CrossRefGoogle Scholar
Jackson, N. and Turner, H. N. 1972. Optimal structure for a co-operative nucleus breeding system. Proceedings of the Australian Society of Animal Production 9: 55–64.Google Scholar
James, J. W. 1977. Open nucleus breeding systems. Animal Production 24: 287–305.Google Scholar
James, J. W. 1978. Effective population size in open nucleus breeding schemes. Ada Agricullurx Scandinavica 28: 387–392.CrossRefGoogle Scholar
James, J. W. 1989. Reviews on molecular and quantitative approaches in honour of Alan Robertson (ed. Hill, W. G. and Mackay, F. C.), pp. 189–234. CAB International, Wallingford, UK.Google Scholar
Kinghorn, B. P. and Shepherd, R. K. 1994. A tactical approach to breedin g for information-rich designs. Proceedings of the 5th world congress on genetics applied to livestock production, Guelph, vol. 18, pp. 255–261.Google Scholar
Mueller, J. P. 1984. Single and two-stage selection on different indices in open nucleus breeding systems. Genetique, Selection, Evolution 16:103–119.CrossRefGoogle ScholarPubMed
Mueller, J. P. and James, J. W. 1983. Effects of reduced variance due to selection in open nucleus breeding systems. Australian Journal of Agricultural Research 34: 53–62.CrossRefGoogle Scholar
Shepherd, R. K. 1991. Multi-tier open nucleus breeding schemes. Ph.D. thesis, University of New England, Armidale.Google Scholar
Shepherd, R. K. and Kinghorn, B. P. 1992. Optimising multi-tier open nucleus breeding schemes. Theoretical and Applied Genetics 85:372–378.CrossRefGoogle ScholarPubMed
Shepherd, R. K. and Kinghorn, B. P. 1993. A deterministic model of BLUP selection in two tier open nucleus breeding schemes. Livestock Production Science 33: 341–354.CrossRefGoogle Scholar
Shepherd, R. K. and Kinghorn, B. P. 1994. A deterministic multi-tier model of assortative mating following selection. Genetics, Selection, Evolution 26: 495–516.CrossRefGoogle Scholar
Shepherd, R. K., Kinghorn, B. P. and Nicol, G. B. 1990. Production and use of ebvs in structured breeding populations. Proceedings of the Australian Society of Animal Production 8: 85–93.Google Scholar
Wray, N. R. and Hill, W. G. 1989. Asymptotic rates of response from index selection. Animal Production 49: 217–227.Google Scholar
Wray, N. R., Woolliams, J. A. and Thompson, R. 1994. Prediction of rates of inbreeding in populations undergoing index selection. Theoretical and Applied Genetics 87: 878–892.CrossRefGoogle ScholarPubMed