Grazing management and nematode parasite control in cattle in the temperate climatic zone of Australia

Abstract

Over 2 years, 1979 and 1981, yearling cattle were grazed from July to December/January on phalaris- or annual ryegrass-based pastures that had been previously grazed by either weaners, cows or cattle drenched every 2 weeks. All yearlings had previously been drenched at weaning in autumn, and from July were either set-stocked, or moved once or twice on to pastures previously grazed by cows. The experiment was conducted at Ginninderra. near Canberra. If a portion of the pasture was saved in winter for grazing in early spring, increased liveweight gains were observed while yearlings grazed the saved area. However, the greater gains during this period were not enough to compensate for previous weight losses or lower gains, so that saving pasture was no better than set-stocking over the total period. In 1979, a year of low rainfall and pasture growth, yearlings drenched 2-weekly gained no more weight than undrenched yearlings, despite much lower worm burdens. In 1981, with average pasture growth, yearlings drenched in July before moving on to pastures previously grazed by cows, and drenched again in September, gained as much weight as those drenched every 2 weeks and significantly more than those undrenched and set-stocked. It is recommended that weaners or yearlings should be moved in July on to improved pastures of low infectivity (obtained by previous grazing with cows or sheep). If combined with one or two drenches, this single move would be as effective for optimising weight gains as more complicated management schemes.