Frequency of anthelmintic drenching of lambs in Waikato

Abstract

Experiments in 1972 in Waikato with anthelmintics on lambs compared six drenches at monthly intervals from January to June inclusive with a drench in March, April, and May, and with no drenching. Drenching improved live-weight gains in winter and resulted in heavier fleeces at spring shearing, lowered incidence of acquired faults in wool, and heavier shorn body weights. After shearing, undrenched lambs showed compensatory growth, but it was insufficient to compensate fully for the earlier retardation, when final weighings were made in January and February. Six drenches were more effective than three, from a slight advantage in winter to more pronounced effects in wool weights and shorn body weights at October shearing. At the final weighings the beneficial effects from six drenches were more marked than from three. Wool- and body-weight increases from more frequent drenching would not necessarily have been financially beneficial.