Skip to main content Accessibility help
×
Home

Genetic relationships between faecal egg count and production traits in commercial Merino sheep flocks

  • G. E. Pollott (a1) and J. C. Greeff (a2)

Abstract

In several countries the gastro-intestinal parasites of sheep show evidence of resistance to the commonly used anthelmintic treatments. The use of animals with genetic resistance to such parasites has been shown to be a viable alternative in a number of resource flocks. However, the genetics of host resistance to parasites in industry flocks and the effects on production traits of using resistant sheep is relatively unknown. This study addresses these questions using data from 55 commercial Merino flocks in Australia. The heritability and genetic correlations were estimated for faecal egg count (FEC), an indicator of host resistance, and eleven fleece and body production traits. The heritability of FEC (0·26 (s.e. 0·018)), using a sire model, was found to be similar to other estimates reported in the literature from resource flocks. The heritabilities of production traits were also consistent with published reports from resource flocks. The genetic correlations between FEC and the 11 production traits, calculated using a sire model, were mostly zero, except for staple strength (-0·17 (s.e. 0·096)), fat depth (-0·26 (s.e. 0·088)) and eye-muscle depth (-0·18 (s.e. 0·091)). Animal model estimates of heritability and the genetic correlations between the traits were largely similar to the sire model estimates. Correlated responses to selection for reduced FEC based on the sire model genetic parameters were calculated to be less than 0·15% of the trait mean per generation for all traits except staple strength, fat depth, muscle depth and live weight. These were expected to increase slightly under selection for reduced FEC. Thus industry-based selection programmes to increase host resistance to parasites should be effective and have no detrimental effect on production characteristics of Merino sheep in Australia. The full benefit of such industry-based schemes could be improved by a better level of recording in the flocks studied.

Copyright

Corresponding author

References

Hide All
Chandrawathania, P., Waller, P. J., Adnan, M. and Hoglund, J. 2003. Evolution of high-level, multiple anthelmintic resistance on a sheep farm in Malaysia. Tropical Animal Health and Production 35: 1725.
Clarke, B. 2002. Review of genetic parameters for Australian Merino sheep. Report to Meat and Livestock Australia; project no. SHGEN. 005.Department of Agriculture of Western Australia, Perth.
Clarke, B., Brown, D. J. and Ball, A. J. 2002. Preliminary genetic parameters for liveweight and ultrasound scan traits in Merinos. Proceedings of the Australian Association of Breeding and Genetics 15: 326330.
Cloete, S. W. P., Schoeman, S. J., Coetzee, J. and Morris, J. de V. 2001. Genetic variances for liveweight and fleece traits in Merino, Dohne Merino and South African Meat Merino sheep. Australian Journal of Experimental Agriculture 41: 145153.
Cole, V. G. 1986. Animal health in Australia, vol. 8: helminth parasites of sheep and cattle. Australian Government Publishing Service, Canberra.
Eady, S. J., Woolaston, R. R. and Barger, I. A. 2003. Comparison of genetic and nongenetic strategies for control of gastrointestinal nematodes of sheep. Livestock Production Science 81: 1123.
Eady, S. J., Woolaston, R. R., Lewer, R. P., Raadsma, H. W., Swan, A. A. and Ponzoni, R. W. 1998. Resistance to nematode parasites in Merino sheep: correlation with production traits. Australian Journal of Agricultural Research 49: 12011211.
Gilmour, A. R., Thompson, R. and Cullis, B. R. 1995. Average information REML, an efficient algorithm for variance parameter estimation in linear mixed models. Biometrics 51: 14401450.
Greeff, J. C. and Karlsson, L. J. E. 1998. The genetic relationship between faecal consistency, faecal worm egg counts and wool traits in Merino sheep. Proceedings of the sixth world congress on genetics applied to livestock production, Armidale, vol. 24, pp. 6366.
Greeff, J. C. and Schlink, A. C. 2001. The inheritance of felting of Merino wool. Proceedings of the Australian Association of Breeding and Genetics 14: 497500.
Hatcher, S. and Atkins, K. D. 2000. Breeding objectives which include fleece weight and fibre diameter do not need fibre curvature. Proceedings of the 23rd biennial conference of the Australian Association for Animal Production, pp. 293296.
Hickson, J. D., Swan, A. A., Kinghorn, B. P. and Piper, L. R. 1995. Maternal effects at different ages in Merino sheep. Proceedings of the Australian Association of Breeding and Genetics 11: 416420.
Hong, C., Hunt, K. R. and Coles, G. C. 1996. Occurrence of anthelmintic nematodes on sheep farms in England and goat farms in England and Wales. Veterinary Record 139: 8386.
Karlsson, L. J. E., Greeff, J. C. and Harris, J. F. 1995. Genetic trends in a selection line for low faecal worm egg count. Proceedings of the Australian Association of Breeding and Genetics 11: 122125.
Maniatis, N. and Pollott, G. E. 2002. Nuclear, cytoplasmic and nuclear effects on growth, fat and muscle traits in Suffolk lambs from a sire referencing scheme. Journal of Animal Science 80: 5767.
Maniatis, N. and Pollott, G. E. 2003. The impact of data structure on genetic (co)variance components of early growth in sheep, estimated using an animal model with maternal effects. Journal of Animal Science 81: 101108.
Melo, A. C. F. L., Reis, I. F., Bevilaqua, C. M. L., Veiria, L. da S., Echevarria, F. A. M. and Melo, L. M. 2003. [Nematodes resistant to anthelmintics in sheep and goat flocks in the State of Ceara, Brazil.] Ciência Rural 33: 339344.
Morris, C. A., Bisset, S. A., Vlassoff, A., Baker, R. L., Watson, T. G. and Wheeler, M. 1997a. Yearling and ewe fleece weights in Romney and Perendale flocks selected for divergence in faecal nematode egg count. Proceedings of the Association for the Advancement of Animal Breeding and Genetics 12: 5053.
Morris, C. A., Vlassoff, A., Bisset, S. A., Baker, R. L., Watson, T. G., West, C. J. and Wheeler, M. 2000. Continued selection of Romney sheep for resistance or susceptibility to nematode infection: estimates of direct and correlated responses. Animal Science 70: 1727.
Morris, C. A., Vlassoff, A., Bisset, S. A., Baker, R. L., West, C. J. and Hurford, A. P. 1997b. Responses of Romney sheep to selection for resistance or susceptibility to nematode infection. Animal Science 64: 319329.
Mortimer, S. I. and Atkins, K. D. 1995. Maternal effects influence growth traits of Merino sheep. Proceedings of the Australian Association of Breeding and Genetics 11: 421424.
Overend, D. J., Phillips, M. L., Poulton, A. L. and Foster, C. E. D. 1994. Anthelmintic resistance in Australian sheep nematode populations. Australian Veterinary Journal 71: 117121.
Taylor, P. J., Atkins, K. D. and Gilmour, A. R. 1999. Genetic association between fibre curvature, staple crimp and wool production and quality of Merino sheep. Proceedings of the Australian Association of Breeding and Genetics 13: 456459.
Whitlock, H. V. 1948. Some modifications of the McMaster helminth egg-counting technique and apparatus. Journal of the Council for Scientific and Industrial Research 21: 177180.
Woolaston, R. R. and Windon, R. G. 2001. Selection of sheep for response to Trichostrongylus colubriformis larvae: genetic parameters. Animal Science 73: 4148.

Keywords

Genetic relationships between faecal egg count and production traits in commercial Merino sheep flocks

  • G. E. Pollott (a1) and J. C. Greeff (a2)

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed