Effect of repeated anthelmintic treatment on weight gain in Hereford and Brahman crossbred cattle in south-eastern Queensland

Abstract

Hereford and Brahman crossbred steers were treated with the injectable anthelmintic, levamisole, at either 3-, 6- or 12-week intervals for 8 months after weaning. Throughout the studies, the different treatment groups were maintained on separate pastures with the exception of 1 group in which half of the animals were treated 3-weekly and the others were untreated. A further untreated group was grazed separately. The trial was repeated with different groups of weaners in 3 successive years. The major gastrointestinal nematodes infecting the cattle were Haemonchus placei, Oesophagostomum radiatum, Cooperia pectinata and Cooperia punctata. The Hereford weaners treated every 3 or 6 weeks showed significantly greater weight gains than untreated steers, but those treated every 12 weeks did not. In 2 of the 3 years. Brahman-cross weaners showed a significant increase in weight gain with the 3-week schedule but not with the 6- and 12-week schedules. Twelve months after treatment ended, the final liveweights of the treated groups did not differ significantly from those of the control groups for either Hereford or Brahman crossbred cattle.