The genetics of resistance and resilience to Haemonchus contortus infection in young merino sheep
GAA Albers, GD Gray, LR Piper, et al.
Int J Parasitol, Vol. 17, pp. 1355-1363, 1987
Abstract
Albers G. A. A., Gray G. D., Piper L. R., Barker J. S. F., Le Jamure L. F. & Barger I. A. 1987. The genetics of resistance and resilience to Haemonchus contortus infection in young Merino sheep. International Journal Parasitology 17: 1355-1363. Young Merino sheep in 60 half-sib groups, totalling over 1000 lambs, were given a single dose of 11,000 Haemonchus contortus larvae. Resistance was measured, together with productivity during infection and when uninfected. One half-sib group exhibited an extremely high level of resistance; its sire was postulated to be the carrier of a major resistance gene. Genetic parameters were estimated for productivity during infection and in the absence of infection, for resistance as measured by faecal egg count and haematocrit, and for resilience as measured by the depression of after infection at 0.4. the heritability of resilience was too low to allow substantial progress by direct selection for this trait. Genetic correlations between resistance to infection and production traits when uninfected were not significantly different from zero. It was concluded that selection for polygenically controlled resistance would lead to substantial progress for this trait and would also increase productivity of infected animals.