Genetic variation in resistance or tolerance to internal nematode parasites in strains of sheep at Rotomahana

T.G. Watson, R.L. Baker and T.G. Harvey

Ruakura Animal Research Station, Ministry of Agriculture and Fisheries, Hamilton and Rotomahana Research Station, Rotorua

Proceedings of the New Zealand Society of Animal Production. 1986, 46: 23-26

Gastrointestinal nematode parasitism is a major concern for animal health and productivity. Studies at Rotomahana Research Station are evaluating the potential of genetic selection of sheep with increased resistance and/or tolerance to parasitism.

Progeny testing of 35 sires in 1984 and 20 of these again during 1985 to investigate strain and sire variation, as well as repeatability in faecal egg counts (FEC), revealed an average heritability estimate of 0.34 ą 0.19 in ewe lambs. Strain and sire rankings were consistent across years and across sexes in 1985 when both wether and ewe lambs were faecal sampled.

Notably, the Ruakura High Fertility Romney strain had the highest FEC and above average live-weight gains yet below average dag score of the 5 strains compared. These results suggest that this line may be tolerant rather than resistant to nematode parasite infection.

Moderate heritabilities for FEC suggest that selection responses could be achieved with Romney sheep. Neither live-weight gain nor dag score was favourably correlated with FEC.

Keywords: NZSAPAB; Resistance; nematode; sheep; strains; breeds; parasites; heritability; correlations

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Last Updated 18-03-1997