Breeding sheep for enhanced resistance to gastrointestinal parasites is a promising strategy to limit the use of anthelmintics as parasite resistance to these molecules is now widespread. This paper presents genetic parameters estimated for resistance and resilience traits in the Blond-faced Manech dairy sheep breed. Two datasets were used. First, rams of the selection scheme were experimentally infected twice with L3 larvae of Haemonchus contortus. Fecal egg counts (FEC) and packed cell volume (PCV) loss were measured 30 days after each infection. Secondly, FEC and PCV of naturally infected ewes were recorded in spring, summer and fall of 2015 and 2016 in farms (1 to 6 measures per ewe). Genetic parameters were estimated for each infection conditions but also between natural and artificial infections thanks to the pedigree connections between the two datasets. In experimental conditions, FEC of rams were moderately heritable in second infection (heritability of 0.35) and were strongly correlated to FEC in first infection (genetic correlation of 0.92). For the ewes in natural conditions, FEC heritability was 0.18. Finally, the genetic correlation between FEC of experimentally challenged rams and FEC of the naturally infected ewes was 0.56-0.84. Our results suggest that genetic selection for enhanced resistance to gastro-intestinal nematodes is feasible using FEC in experimental infection measured on rams to improve the parasitism resistance of ewes on farms. It is of interest for the breeders’ organization to measure FEC on rams in order to have standardized measures and allow a better diffusion of the genetic progress in farms. Keywords: gastrointestinal parasites, genetic resistance, genetic parameters, dairy sheep
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Biology - Disease Resistance 2, , 537, 2018
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