Genetic resistance to infections by gastrointestinal nematodes in small ruminants: a sustainability issue for grass-based production systems

Abstract

The resistance of small ruminants to gastro-intestinal nematode infection can be included into a genetic selection program. This resistance can be measured by faecal nematode egg counts. This trait is heritable and only lightly correlated to other selected traits. Faecal egg counts should be measured on a large number of small ruminants in order to be included in selection schemes and this requires the services of a phenotyping platform. The evolution of the nematode community under the selection pressure due to an increase in host resistance should be controlled in order to prevent a putative adaptation of nematodes. In order to avoid adaptation of the parasites, an integrated strategy should be implemented and genetic selection for resistance to nematodes should be associated with the use of anthelmintics, as well as an adequate fulfillment of nutritional needs of small ruminants and adequate management of pastures to reduce infection risk.