Abstract

FlNDGENE is a mixed inheritance model computer program which can analyse extensive animal pedigrees. It partitions the observed variance into fixed effects. polygenic inheritance, a two allele major locus effect and a residual envimnmental variance. It do-es not require genotype information. Data from three New Zealand sheep experiments where faecal nematode egg count (FEC) information had been collected were examined by this method. They included a long term selection experiment for FEC in Rornneys at Wallaceville, another in Perendales at Ruakura, and a randomly mated Coopworth flock at Woodlands Research Station. All PEC traits were initially transformed using the function log.(x+lOO). The final model included the effect of sex/year contemporary group, birthday and polygenic inheritance in addition to a 2 allele Mendelian gene effect. Results from all three data sets suggested a dominant a’utosomal gene for host susceptibility was affecting strongyle PEC values in the summer/autumn period with estimates of 0.37,0.69 and 0.72 log eggs/g for the single allele effect from Romney, Perendale and Coopworth flocks respectively. Corresponding values for dominance were 0.47,0.44 and 0.88 log eggs/g with susceptible allele frequency 0.14.0.55 and 0.69. When considered together, these results suggest that at least one QTL is affecting the development of host resistance to internal parasites in young sheep. The identification and characterisation of this QTL may result in useful novel methods of internal parasite control.

JC, McEwan, CA Morris, SA Bisset, and RJ Kerr

Proceedings of the New Zealand Society of Animal Production, Volume 57, , 290-294, 1997