Effect of Haemonchus contortus on productivity of ewes, lambs and weaners in a semi-arid environment

Lactating ewes, ewes that had lambed but subsequently lost their lambs (dry) and weaners were either artificially infested with 2000-3000 third-stage Haemonchus contortus larvae (parasitized) or drenched with levamisole (treated) and run under extensive grazing conditions in north-west Queensland. Worm egg counts in parasitized lactating, dry and weaner sheep ranged from 860-2830 eggs per gram of faeces. These levels of infestation significantly (P<0.01) reduced liveweight gain of all three sheep classes, milk yield of ewes and wool growth of weaners compared to their treated counterparts