Hostname: page-component-78c5997874-xbtfd Total loading time: 0 Render date: 2024-11-10T22:15:57.375Z Has data issue: false hasContentIssue false
  • English
  • Français

MOET breeding schemes for wool sheep 1. Design alternatives

Published online by Cambridge University Press:  02 September 2010

N. R. Wray  and
M. E. Goddard
N. R. Wray
Affiliation:
Livestock Improvement Unit, Victorian Institute of Animal Science, 475 Mickleham Road, Attwood 3049, Victoria, Australia
M. E. Goddard
Affiliation:
Livestock Improvement Unit, Victorian Institute of Animal Science, 475 Mickleham Road, Attwood 3049, Victoria, Australia
Get access

Abstract

Breeding schemes for ivool sheep based on natural service (N), MOET (multiple ovulation and embryo transfer) in adults (A) and MOET in juveniles (J) are compared using Monte Carlo simulation allowing overlapping generations and selection across age groups. In all schemes parents can be a maximum of 6 years old when their offspring are born, and can be a minimum of 2 years in N or A schemes or 1 year in f schemes. Embryo transfer success rates follow realistic distributions (only 70% of flushes resulting in live lambs) with a mean of 2·13 or 345 6-month-old lambs per donor per flush for current or ‘future’ situations. Under natural mating an average of 1·09 6-month-old lambs per ewe mated is assumed. The trait under selection has a heritability of 0·4 and is measurable on both sexes by 18 months of age, which is before selection in N and A schemes but after the initial opportunity for selection in f schemes where selection is based on a pedigree index. Two culling policies for males are considered in J schemes: all sires culled if not selected (J), or all sires available for selection after their record is collected even if they were not selected on their pedigree index in the previous year (f o ). Comparison of schemes is made on the basis of response depressed by the effect of inbreeding and cumulated and discounted over a medium time horizon. For a given population size (constant expected number of lambs per year and therefore numbers of dams dependent on fertility rates) different numbers of sires were utilized. The optimum number of sires was determined as the number which maximized the response criterion. N, A, J and J° schemes have different optimum numbers of sires (5, 8,30 and 20 respectively) which occur at different rates of inbreeding and which are approximately independent of population size. Advantages in the response criterion of A, J and J° over N schemes are 23%, 33% and 47% respectively for ‘future’ embryo transfer success rates and mass selection. Increasing the number of lambs born per donor ewe from 2·13 to 13·8 (by increasing embryos per flush and number of flushes) increases the response criterion by up to 25% in A and up to 11% in J schemes (assuming donor ewes are mated to a different sire for each flush) with 345 lambs born per year. Use of best linear unbiased prediction (BLUP) estimated breeding values increases response by 8%, 3% and 3% in N, A and J schemes respectively. The advantages off over A and N schemes, of increased lambs per donor and of BLUP over mass selection all increase as population size increases. Insemination of the poorer ewes with semen which gave only female offspring gave 5% increase in the N scheme and no benefit in A or f schemes.

Keywords

best linear unbiased predictioninbreedingMOETselectionsheepwool
Type
Research Article
Information
Animal Production , Volume 59 , Issue 1 , August 1994 , pp. 71 - 86
Copyright
Copyright © British Society of Animal Science 1994

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Amman, R. P. 1989. Treatment of sperm to predetermine sex. Theriogenology 31: 49–60.CrossRefGoogle Scholar
Atkins, K. D. 1990. Incorporating parameters for lifetime productivity into breeding objectives for sheep. Proceedings of the fourth world congress on genetics applied to livestock production, Edinburgh, vol XV, pp. 17–26.Google Scholar
Bulmer, M. G. 1971. The effect of selection on genetic variability. American Naturalist 105: 201–211.CrossRefGoogle Scholar
Colleau, J. J. 1991. Using embryo sexing within closed mixed multiple ovulation and embryo transfer schemes for selection on dairy cattle. journal of Dairy Science 74: 3973–3984.CrossRefGoogle ScholarPubMed
Gaffney, B., Wade, C. M., Goddard, M. E. and Nicholas, F. W. 1991. Genetic and economic value of multiple ovulation and embryo transfer in nucleus Merino flocks. Proceedings of the Australian Association of Animal Breeding and Genetics 9: 101–105.Google Scholar
Goddard, M. E. 1992. Optimal effective population size for the global population of black and white dairy cattle. journal of Dairy Science 75: 2902–2911.CrossRefGoogle ScholarPubMed
James, J. W. 1972. Optimum selection intensity in breeding programmes. Animal Production 14: 1–9.Google Scholar
Jodar, B. and Lopez-Fanjul, C. 1977. Optimum proportions selected with unequal sex numbers. Theoretical and Applied Genetics 50: 57–61.CrossRefGoogle ScholarPubMed
Juga, J. and Mäki-Tanila, A. 1987. Genetic change in a nucleus breeding dairy herd using embryo transfer. Ada Agriculturae Scandinavica 37: 511–519.CrossRefGoogle Scholar
Keller, D. S., Gearheart, W. W. and Smith, C. 1990. A comparison of factors reducing selection response in closed nucleus breeding schemes. journal of Animal Science 68: 1553–1561.Google Scholar
Lamberson, W. R. and Thomas, D. L. 1984. Effects of inbreeding in sheep: a review. Animal Breeding Abstracts 52: 287–297.Google Scholar
Land, R. B. and Hill, W. G. 1975. The possible use of superovulation and embryo transfer in cattle to increase response to selection. Animal Production 21: 1–12.Google Scholar
Lohuis, M. M., Smith, C. and Dekkers, J. C. M. 1993. MOET results from a dispersed hybrid nucleus programme in dairy cattle. Animal Production 57: 369–378.Google Scholar
McClintock, A. E. and Cunningham, E. P. 1974. Selecting in dual purpose cattle populations: defining the objective. Animal Production 18: 237–247.Google Scholar
McClintock, A. E. and Nicholas, F. W. 1992. The implications of advanced breeding techniques. Australian Meat and Livestock Research and Development Corporation, Sydney.Google Scholar
Maxwell, W. M. C., Szell, A., Hunton, J. R. and Ryan, J. P. 1990. Artificial breeding: embryo transfer and cloning. In Reproductive physiology of Merino sheep: concepts and consequences (ed. Oldham, C. M., Martin, G. B. and Purvis, I. W.), pp. 217–237. School of Agriculture (Animal Science), The University of W. Australia.Google Scholar
Nicholas, F. W. and Smith, C. 1983. Increased rates of genetic change in dairy cattle by embryo transfer and splitting. Animal Production 36: 341–353.Google Scholar
Quinton, M., Smith, C. and Goddard, M. E. 1992. Comparison of selection methods at the same level of inbreeding. Journal of Animal Science 70: 1060–1067.CrossRefGoogle ScholarPubMed
Rangel-Santos, R., McDonald, M. F. and Wickham, G. A. 1990. Practical difficulties of a juvenile MOET scheme. Proceedings of the Australian Association of Animal Breeding and Genetics 8: 543–544.Google Scholar
Ruane, J. 1991. The importance of family sizes in adult multiple ovulation and embryo transfer (MOET) nucleus breeding schemes in dairy cattle. Animal Production 52: 33–47.Google Scholar
Scaramuzzi, R. J., Geldard, H., Beels, C. M., Hoskinson, R. M. and Cox, R. I. 1983. Increased lambing percentages through immunization against steroid hormones. Wool Technology and Sheep Breeding 31: 87–97.Google Scholar
Smith, C. 1986. Use of embryo transfer in genetic improvement of sheep. Animal Production 42: 81–88.Google Scholar
Swan, A. A., Woolaston, R. R. and Piper, L. R. 1992. Establishing a centralised database for Merino sire evaluation schemes. Proceedings of the Australian Association of Animal Breeding and Genetics 10: 490–493.Google Scholar
Toro, M. A., Nieto, B. and Salgado, C. 1988. A note on minimisation of inbreeding in small scale selection programmes. Livestock Production Science 20: 317–323.CrossRefGoogle Scholar
Wade, C. and Goddard, M. E. 1993. How much is a genetically superior ram worth? Australian Journal of Agricultural Research 45: 403–413.Google Scholar
Woolliams, J. A. 1989. Modifications to MOET nucleus breeding schemes to improve rates of genetic progress and decrease rates of inbreeding in dairy cattle. Animal Production 49: 1–14.Google Scholar
Woolliams, J. A., Wray, N. R. and Thompson, R. 1993. Prediction of long-term contributions and inbreeding in populations undergoing mass selection. Genetical Research, Cambridge 62: 231–242.CrossRefGoogle 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. and Simm, G. 1990. The use of embryo transfer to accelerate genetic improvement in beef cattle. Proceedings of the fourth world congress in genetics applied to livestock production, Edinburgh, vol XV, pp. 315–322.Google Scholar