Finding disease resistance QTL in sheep

Long term divergent selection lines for resistance and susceptibility to two diseases of sheep were utilized to look for disease resistance QTL. The diseases were facial eczema, which is caused by a saprophytic fungus of pasture which produces toxic spores, and gastro-intestinal parasitic nematodes. Sires derived from reciprocal crosses of the lines were mated with unrelated dams to generate large half-sib pedigrees, which were then measured for traits known to be related to the disease of interest. Subsequently, animals from the tails of the distribution for the primary disease trait have been genotyped and the inheritance of the sires alleles examined for evidence of segregation. We have also used the same pedigrees and the original divergent selection lines to examine the segregation of candidate genes to determine their possible involvement in disease resistance. Preliminary results suggest that both experiments have been successful, but via alternative methodologies.