MANAGEMENT FACTORS AFFECTING PARASITISM AND PRODUCTION OF PRIME LAMBS

When nematode infection was controlled by anthelmintic treatment, prime lambs from ewes stocked on sown pasture at 10 ewes/ha reached marketable weights (30-34 kg) at 14-18 weeks of age. Untreated lambs carried an average of 5,000, worms, which did not significantly affect liveweight production. Lambs from ewes stocked at 20/ha required an additional 14-15 weeks to reach 30-36 kg and by this time untreated lambs had mean worm counts of 20,000 and liveweight production loss was 4-6 kg (P < 0.001). Application of nitrogen fertilizer to lambing paddocks of sown pasture had no effect on levels of parasitism in lambs. At stocking rates of 10 and 15 ewes/ha the live weights of lambs were lower (P < 0.01) in the fertilized than in the control paddocks. I