Abstract

Gastrointestinal nematodes infect sheep grazing in contaminated pastures leading to reduced growth and productivity. Parasite control using anthelmintics is being questioned due to the development of nematode strains resistant to one or multiple classes of drugs (Sangster, 1999). Another aspect to consider is the increasing demand of consumers for products free of residues that might enter the food chain from the environment (Herd et al., 1993). Selecting animals naturally resistant to these parasites constitutes an alternative to complete reliance on drugs.  
 
Resistance to nematode parasites is associated with the development of an early immune response. The control of the type, rapidity and size of this response is very complex and involves many genes. However, it is possible that only a few play a significant role in the resistance process. An efficient first step towards the identification of these genes is the detection of the chromosomal regions where they are located, using a quantitative trait loci (QTL) finding approach. A previous study (Beh et al., 1998) showed evidence of QTL segregation for nematode resistance on sheep chromosome 1. As a part of a project that aims to identify the loci responsible for parasite resistance in sheep, we have undertaken the study of this chromosome as a candidate for QTL segregation using an outcross population.  

C. Diez-Tascon, P. A MacDonald, K. G Dodds, John C McEwan, A. M Crawford

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 2002. Session 13, , 13.37, 2002
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