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Genetic and epidemiological relationships between productivity and disease resistance: gastro-intestinal parasite infection in growing lambs

Published online by Cambridge University Press:  18 August 2016

S. C. Bishop  and
M. J. Stear
S. C. Bishop
Affiliation:
Roslin Institute (Edinburghi Roślin, Midlothian EH25 9PS
M. J. Stear
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
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Abstract

This paper demonstrates how interactions between host genotype for resistance to an infectious disease and the epidemiology of that disease can have large influences on animal productivity and hence on breeding goals for domestic livestock. This is illustrated for the case of gastro-intestinal parasitism in lambs. A model of the parasite infection was developed to include between-animal variation (genetic, permanent and temporary environmental) for live-weight gain, food intake, larval establishment rate in the host, worm fecundity and worm mortality rate. Achieved live-weight gain was defined as the sum of potential live-weight gain under conditions of no parasite infection, a trait correlated with food intake and growth-rate reduction due to the infection. The reduction in growth-rate was calculated from cumulative larval challenge and cumulative worm mass in the lamb. Genetic parameters were then estimated for the output traits of observed live weight at 6 months of age, growth rate reduction and faecal egg count. Model parameters were chosen so that the output means and heritabilities for faecal egg count and live-weight gain mimicked field data for Scottish Blackface lambs and growth-rate reductions were proportionately 0·25 , on average. The model predicted a weak phenotypic correlation (mean = -0·10) between observed live weight and faecal egg count, the indicator of resistance but a stronger favourable (negative) genetic correlation between these traits (mean = -0·27). The severity, or epidemiology, of the disease greatly influenced the results - the genetic correlation between observed live weight and faecal egg count strengthened from -0·02 to -0·46 as the disease severity changed from mild to severe. Selection for reduced faecal egg count resulted in large correlated increases in live-weight gain, more than twice that predicted by quantitative genetic theory, due to the reductions in growth rate losses as the disease challenge to the animals decreased. Conversely, selection for increased live-weight gain resulted in reductions in faecal egg count close to expectations. This asymmetry of selection response emphasizes the epidemiological benefits obtainable from selection for resistance to infectious chronic diseases - such selection will result in improvements in both animal health and productivity not seen when selection is for improved productivity, alone. Breeding goals should be designed to take account of such effects.

Keywords

disease resistanceepidemiologyparasites (gastro-intestinal)selectionsheep
Type
Research Article
Information
Animal Science , Volume 69 , Issue 3 , December 1999 , pp. 515 - 524
Copyright
Copyright © British Society of Animal Science 1999

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References

Albers, G. A. A., Gray, G. D., Piper, L. R., Barker, J. S. F., Le Jambre, L. F. and Barger, I. A. 1987. The genetics of resistance and resilience to Haemonchus contortus infection in young Merino sheep. International Journal for Parasitology 17: 1355–1363.CrossRefGoogle ScholarPubMed
Bishop, S. C., Bairden, K., McKellar, Q. A., Park, M. and Stear, M. J. 1996. Genetic parameters for faecal egg count following mixed, natural, predominantly Ostertagia circumcincta infection and relationships with live weight in young lambs. Animal Science 63: 423–428.CrossRefGoogle Scholar
Bishop, S. C. and Stear, M. J. 1997. Modelling responses to selection for resistance to gastro-intestinal parasites in sheep. Animal Science 64: 469–478.Google Scholar
Bisset, S. A., Vlassof, A., Morris, C. A., Southey, B. R., Baker, R. L. and Parker, A. G. H. 1992. Heritability of and genetic correlations among faecal egg counts and productivity traits in Romney sheep. New Zealand Journal of Agricultural Research 35: 51–58.Google Scholar
Coop, R. L., Graham, R.B., Jackson, F., Wright, S. E. and Angus, K. W. 1985. Effect of experimental Ostertagia circumcincta infection on the performance of grazing lambs. Research in Veterinary Science 38: 282–287.CrossRefGoogle ScholarPubMed
Coop, R. L. and Holmes, P. H. 1996. Nutrition and parasite interaction. International Journal for Parasitology 26: 951–962.CrossRefGoogle ScholarPubMed
Coop, R. L., Sykes, A. R. and Angus, K. W. 1977. The effect of daily intake of Ostertagia circumcincta larvae on body weight, food intake and concentration of serum constituents in sheep. Research in Veterinary Science 23: 76–83.CrossRefGoogle ScholarPubMed
Coop, R. L., Sykes, A. R. and Angus, K. W. 1982. The effect of three levels of Ostertagia circumcincta larvae on growth rate, food intake and body composition of growing lambs. Journal of Agricultural Science, Cambridge 98: 247–255.CrossRefGoogle Scholar
Douch, P. G. C., Green, R. S., Morris, C. A., Bisset, S. A., Vlassof, A., Baker, R. L., Watson, T. G., Hurford, A. P. and Wheeler, M. 1995. Genetic and phenotypic relationships among anti-Trichostrongylus colubriformis antibody level, faecal egg count and body weight traits in grazing Romney sheep. Livestock Production Science 41: 121–132.Google Scholar
Eady, S.J. 1998. Worm resistance in a Merino breeding objective — influence of genetic correlations between resistance and production traits. Proceedings of the sixth world congress on genetics applied to livestock production, Annidale, vol. 27, pp. 141–144.Google Scholar
Gilmour, A. R., Thompson, R., Cullis, B. R. and Welham, S. 1996. ASREML. Biometrics bulletin no. 3, NSW Agriculture.Google Scholar
Houtert, M. F. J. van and Sykes, A. R. 1996. Implications of nutrition for the ability of ruminants to withstand gastro-intestinal nematode infections. International Journal for Parasitology 26: 1151–1167.Google Scholar
Leathwick, D. M., Barlow, N. D. and Vlassof, A. 1992. A model for nematodiasis in New Zealand lambs. International Journal for Parasitology 22: 789–799.CrossRefGoogle Scholar
McAnulty, R. W., Clark, V. R. and Sykes, A. R. 1982. The effect of clean pasture and anthelmintic frequency on growth rates of lambs on irrigated pastures. Proceedings of the New Zealand Society of Animal Production 42: 187–188.Google Scholar
McEwan, J. C., Mason, P., Baker, R. L., Clarke, J. N., Hickey, S. M. and Turner, K. 1992. Effect of selection for productive traits on internal parasite resistance in sheep. Proceedings of the New Zealand Society of Animal Production 52: 53–56.Google Scholar
McEwan, J. C., Dodds, K. G., Gréer, G. J., Bain, W. E., Duncan, S. J., Wheeler, R., Knowler, K. J., Reid, P. J., Green, R. S. and Douch, P. G. C. 1995. Genetic estimates for parasite resistance traits in sheep and their correlations with production traits. New Zealand Journal of Zoology 22: 177.Google Scholar
MacKenzie, K. and Bishop, S. C. 1998. A genetic epidemiological model of pig disease resistance. Proceedings of the sixth world congress on genetics applied to livestock production, Annidale, vol. 27, pp. 287–290.Google Scholar
Morris, C. A. 1998. Responses to selection for disease resistance in sheep and cattle in New Zealand and Australia. Proceedings of the sixth world congress on genetics applied to livestock production, Armidale, vol. 27, pp. 295–302.Google Scholar
Morris, C. A., Vlassof, A., Bisset, S. A., Baker, R. L. and Watson, T. G. 1997a. Direct responses to selection for divergence in faecal nematode egg count in young Romney and Perendale sheep. Proceedings of the Association for the Advancement of Animal Breeding and Genetics, vol. 12, pp. 413–416.Google Scholar
Morris, C. A., Vlassof, 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: 319–329.Google Scholar
Piper, L. R. and Barger, I. A. 1988. Resistance to gastro-intestinal strongyles: feasibility of a breeding program. Proceedings of the third world congress on sheep and beef cattle, pp. 593–611.Google Scholar
Stear, M. J., Bishop, S. C., Bairden, K., Duncan, J. L., Gettinby, G., Holmes, P. H., McKellar, Q. A., Park, M., Strain, S. and Murray, M. 1997. The heritability of worm burden and worm fecundity in lambs following natural nematode infection. Nature 389: 27.Google Scholar
Stear, M. J., Bishop, S. C., Doligalska, M., Duncan, J. L., Holmes, P. H., Irvine, J., McCririe, L., McKellar, Q. A., Sinski, E. and Murray, M. 1995. Regulation of egg production, worm burden, worm length and worm fecundity by host responses in sheep infected with Ostertagia circumcincta . Parasite Immunology 17: 643–652.CrossRefGoogle ScholarPubMed
Woolaston, R. R. and Eady, S. J. 1995. Australian research on genetic resistance to nematode parasites. In Breeding for resistance to infectious diseases in small ruminants (ed. Gray, G. D., Woolaston, R. R. and Eaton, B. T.), pp. 53–75. Australian Centre for International Agricultural Research, Canberra.Google Scholar
Woolaston, R. R. and Piper, L. R. 1996. Selection of Merino sheep for resistance to Haemonchus contortus: genetic variation. Animal Science 62: 451–460.Google Scholar