Integrated parasite management improves control of gastrointestinal nematodes in lamb production systems in a high summer-rainfall region, on the Northern Tablelands, New South Wales

Abstract

This experiment tested the hypothesis that integrated parasite management (IPM) programs would reduce the effects of gastrointestinal nematodes (GIN) in meat-breed lamb production systems on the Northern Tablelands of New South Wales. The experiment was a longitudinal experiment using twin-bearing Border Leicester × Merino ewes on farms managed in accordance to either regional WormBoss IPM programs (n = 3 farms) or typical (TYP) regional GIN control (n = 2 farms). Ewes on each farm were either GIN-suppressed (SUP; n = 120 ewes) or not (NSUP; n = 120 ewes) and were managed in two groups (n = 120/group) balanced for GIN control. Ewes lambed in September and at lamb marking, 120 lambs (Dorset sires) from each ewe GIN control group were enrolled in the experiment to investigate the effect of ewe GIN control on lamb performance up to weaning. Overall mean worm egg count (WEC) of ewes (P = 0.004) was lower with IPM (IPM 766 vs TYP 931 epg) and was achieved with fewer drenches (IPM 4.5 vs TYP 5.5/year). Despite lower WEC, GIN infection reduced liveweight (IPM –2.1 kg vs TYP –1.1 kg, P = 0.0006) and clean fleece weight (IPM –0.11 kg vs TYP –0.01 kg, P = 0.03) of ewes to a greater extent on IPM farms. The annual rate of apparent ewe mortality was 6.5% and this was unaffected by GIN infection. WEC of lambs at weaning was lower on IPM farms (IPM 159 epg vs TYP 322, P < 0.0001) but the difference in weaning weights of lambs reared by NSUP and SUP ewes was greater on IPM farms (IPM –1.1 kg vs TYP 0.2 kg, P < 0.0001). Overall, the production loss due to GIN infection in these sheep-meat production systems, on the Northern Tablelands of New South Wales, was small and treatment frequency can be reduced by IPM programs.