Abstract
The effect of feeding regime on daily liveweight change and eligibility for first service was investigated using 40 Brahman heifers, 22 ± 1.3 months old and 253.7 ± 3.9 kg initial liveweight, given two nutritional treatments during the dry season. Treatment 1 (T1) consisted of rotational grazing on Hypharrenia rufa (Nees) Stapf pastures and Treatment 2 (T2) comprised whole chopped sugar cane, urea and rice polishings fed in confinement. The trial ended on the last date that heifers could enter service under the constraints of a seasonal calving pattern. T2 heifers grew at 0.35 kg day-1 which was significantly different (P<0.001) from T1 heifers which lost 0.07 kg day-1. Chi squared analysis showed that a significantly higher proportion (P<0.001) for the T2 group (60%) than of the T1 group (5%) were eligible for service based on 300 kg minimum liveweight. Analysis of costs and benefits, using a herd production model, showed an increased production of 12.7 kg Lwt LSU-1 yr-1 and increased net income of US$8.85 LSR-1 yr-1 as a result of reducing age at first service from 38 to 26 months by feeding the sugar cane diet during the dry season prior to first service. Sensitivity analysis of changes in sugar cane price showed that under the economic conditions described the opportunity cost of whole cane at the farm gate could rise by 500% before feeding became uneconomic.
