The effect of dry season feeding on the growth of Mashona steers of two ages kept on natural pasture during the subsequent wet season

Mashona steers initially aged eight (weaners; mean weight 177kg) and 20 months (long weaners; mean weight 287kg) were used. Each age group comprised 50 steers. Within age group, 10 steers were slaughtered at the start of the trial to estimate initial measurements of carcass and non-carcass components. One half of the remainder (n=20) were either fed 250g cottonseed meal (CSM) per 100kg liveweight or were not fed CSM during the dry season (June to October). At the end of the dry season, 10 steers were slaughtered from each treatment group and the remainder were slaughtered in May at the end of the subsequent wet season to measure compensatory growth. During the dry season, weaners fed CSM gained 108 g/day while those not fed lost 124 g/day. Corresponding weight changes for long weaners were 150 and 180 g/day, respectively. During the subsequent wet season liveweight gains were 354 and 386 g/day for previously fed and non-fed weaners, respectively, while corresponding weight gains in long weaners were 400 and 447 g/day. Carcass weight change showed a similar pattern. Differences in liveweight between fed and non-fed weaners were 30.5 kg at the end of the dry season and 23.6kg at the end of the subsequent wet season. In long weaners the differences were 39.3kg and 29.0kg, respectively. Carcass weight differences between the fed and non-fed weaners were 16.7kg at the end of the dry season and 12.2kg at the end of the wet season, while corresponding differences for long weaners were 29.5kg and 14.9kg. Non-fed steers slaughtered at the end of the dry season had shorter carcasses, smaller M. longissimus dorsi area, less fat and lower weights of non-carcass components than fed steers. For steers slaughtered at the end of the wet season, differences were generally not significant within age group. The results show that while differences due to CSM were only partially reduced for both liveweight and carcass weight, recovery of the non-carcass components was complete