Age of Weaning and Parasitism in Merino Lambs

Merino lambs born in September and October 1964 were weaned at 4, 6 and 11 weeks of age, at average liveweights of 9 kg, 12 kg, and 19 kg respectively, on to a pasture of phalaris and white clover. The lambs remaining with their mothers for 11 weeks showed the earliest onset of an appreciable worm infection which reached a peak in December about one month after weaning. Similar levels of infection were not reached in the other groups until about two months later. It is concluded that weaning at 4 or 6 weeks of age helped to control roundworm infection in the lambs.