Calf Management Strategies and Reproductive Performance in a Northern Australian Cattle Herd

One hundred and sixty seven Droughtmaster cows with calves were used in two experiments to evaluate the effect of early weaning and creep feeding on cow reproduction rates. Weaning of calves that weighed 48-92 kg instead of the conventional weaning weight of about 180 kg improved cow live weights and increased pregnancy rates by 48% at weaning. The early weaned calves were raised on Stylosanthes hamata (cv. Verano) hay plus a maize based supplement containing no additive, 70 mg/hd/d monensin or 70 mg/hd/d avoparcin. Calf growth rate and feed efficiency were not significantly affected by the rumen modifiers. The creep feeding of calves did not significantly alter cow or calf live weights. There was a 20% increase in cow pregnancy rates with creep feeding of calves even though phosphorus deficiency was observed in a creep-fed group.