No evidence for a universal association between variation in faecal egg count for a mixed field-challenge of gastrointestinal parasites and the presence of the Ovar-DQA1 null haplotype in sheep
2010
Forrest, R.H.J. | Zhou, H. | Fang, Q. | Smyth, A. | Frampton, C.M. | Hickford, J.G.H.
We tested the association of the Ovar-DQA1 null haplotype with faecal egg count (FEC) in 4676 male lambs sourced from 185 different sire-lines and four breeds. For each lamb a faecal sample was collected at weaning (approx. 4 months of age) and mid-autumn (approx. 9 months of age) and each was typed for the presence of Ovar-DQA1 null. General Linear Mixed Models (GLMMs) were used to analyse the relationship between FEC and Ovar-DQA1 null, both across and within breeds. Two models were used, the first testing the effect of the presence/absence of Ovar-DQA1 null and the second testing the effect of the number of copies of Ovar-DQA1 null present in an animal's genotype (i.e. dominant/recessive or additive effects). Across the breeds, no significant effect of the presence of Ovar-DQA1 null on FEC for Nematodirus sp., Strongyle genera, or total FEC was detected at either 4 or 9 months of age using either of the models. Within breeds, significant associations were detected at 4 months in South African Meat Merinos, with the presence of Ovar-DQA1 null in an animal's genotype being associated with a lower strongyle (absent: n =23, geometric mean=135epg; present: n =10, geometric mean=67epg; P =0.025) and total FEC (absent: n =23, geometric mean=220epg; present: n =10, geometric mean=121epg; P =0.017). These associations were not detected at 9 months of age.
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