Rearing dairy calves on irrigated tropical pastures. 2. Effect of levels of maize and cottonseed meal on growth of weaner calves

Abstract

Fifty-two Australian Friesian Sahiwal (AFS) calves were weaned at 70 kg liveweight onto irrigated and fertilised couch (Cynodon dactylon)- pangola (Digitaria decumbens) pastures in North Queensland. They were offered supplements of maize (9.5% crude protein) or a mixture of 5 maize: 1 cottonseed meal (15% crude protein) fed at 1.0 or 1.5 kg/calf.day in a 2 x 2 factorial experiment. Calves entered the experiment after weaning and were removed when they exceeded 130 kg liveweight. More calves were reared in spring and summer than in autumn and winter, and stocking rate varied between 20 weaners/ha (summer) and 12.5 weaners/ha (winter). Additional supplementation with maize above 1 kg/calf.day did not increase liveweight gain in calves of up to 130 kg liveweight. Inclusion of cottonseed meal in the supplement increased calf growth at the higher level of supplementation (P<0.01) and calves reached 130 kg liveweight 2 weeks earlier than calves fed maize (P<0.05). The interaction of level of feeding with protein content of the supplement was significant at P = 0.058. Calves reared in the wet season gained less (0.47 kg/day) than calves reared in the dry season (0.60 kg/day) (P<0.01). Animal responses to supplementary feeding were similar in both seasons, but even at high levels of supplementation, and with added protein, calves reared in the wet season did not maintain desired growth rates over this period.