Genetics of resilience to nematode parasites in Romney sheep

摘要

Abstract 7533 Romney lambs, born in 1991 on six farms in the southern North Island of New Zealand, were studied as part of an investigation into the feasibility and implications of breeding sheep whose lambs require minimal anthelmintic treatment to maintain acceptable performance when exposed to challenge by nematode parasites ("resilience"). They were the progeny of 123 different sires. All flocks involved were genetically linked by the use of reference sires so that analyses could be carried out across farms. After weaning, ram lambs were mustered on 4 or 5 occasions for anthelmintic treatment. Treatment was administered on an individual basis as dictated by body condition and degree of breech‐soiling ("selective drenching"). Drench requirement data including age at first drench (normalised by transformation to include the 5% of animals not requiring drench treatment), 5 binary scores denoting whether or not a lamb was drenched by Time 1, Time 2 … Time 5 ("BY1, BY2… BY5"), and total number of drench tr...