We studied genetics of tolerance and resistance to nematodes in 962 Blackface lambs. A bivariate analysis was performed where tolerance was modeled as genetic effect for slope of reaction norm of bodyweight (BW) on faecal egg count (FEC) and resistance as genetic effect on levels of IgA against larvae (IgA). We observed a negative genetic correlation between BW at low and high FEC suggesting that different sets of genes control BW at low and high FEC. We observed a positive genetic correlation between BW at zero FEC level and IgA indicating that animals with high BW at zero FEC have genetically higher IgA level. We observed a negative genetic correlation between IgA and the slope of the reaction norm indicating that genetically more resistant animals are genetically less tolerant and vice versa. These results provide insight into genetics of tolerance and resistance.

Hamed Rashidi, Han A Mulder, Johan AM van Arendonk, Mart CM de Jong, Michael J Stear

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Genetics of Trait Complexes: Disease resistance, , 096, 2014
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