G.B. ROBBINS G.J. BUSBY and G.B. FAULKNER
Milk production of commercial dairy cows and liveweight gain of beef steers grazing annual pastures of irrigated ryegrass (Lolium spp.) were measured in two experiments in the Burnett district of south-east Queensland. Ryegrass was autumn sown in 1974 and 1975, irrigated about 450 mm total) and nitrogen fertilised (total of 640 and 460 kg N ha-1 respectively) until early December. Both experiments were strip-grazed for ten, three-weekly grazing cycles by varying numbers of cattle according to pasture growth.
Maximum ryegrass growth rates occurred in early spring and averaged about 130 kg ha-1 day-1 in Experiment 1 and about 105 kg ha-1 day-1 in Experiment 2. Stocking densities generally reflected pasture growth rates, reaching 9.5 and 6.0 beasts ha-1 during spring in Experiments 1 and 2 respectively. Animal production was not limited by nitrogen or phosphorus content of the pasture on offer.
Milk production on ryegrass for 207 days was 13.2 kg cow-1 day-1, similar to that from cows grazing commercial pastures of paspalum, clover and oats on the same farm. With the high average stocking rate on ryegrass (7.6 cows ha-1) milk production per hectare was 20,890 kg, approximately double that from the commercial pastures.
Beef steers with mean initial weight of 374 kg, stocked at an average of 5.4 beasts ha-1 gained 0.8 kg head-1 day-1 and were ready for slaughter at an average weight of 448 kg head-1.