Non-esterified fatty acids (NEFA) and glucose concentrations in the plasma of 9 lambs weaned from 3.5 to 9.5 weeks of age were compared with the concentrations found in 2 lambs suckling the ewe. Lambs weaned at 3.5 weeks had markedly elevated plasma NEFA concentrations for up to 3 weeks after weaning. A similar trend was apparent for 2 days after lambs were weaned at 5.5 weeks of age. There was a highly significant negative correlation between plasma NEFA and energy intake in these groups of lambs for 30 days after weaning. The relationships for the later-weaned groups were not significant. Weaning caused an immediate decrease in the plasma glucose concentration, irrespective of the age of the lamb. Glucose then increased slightly, but subsequently declined with time. It was concluded that very early weaning resulted in mobilisation of body fat in response to a low energy intake.

Lambs were weaned at 3.5, 5.5, and 7.5 weeks of age and fed on lucerne or ryegrass-clover pasture for periods of 2 to 8 weeks. Energy gain was determined by the comparative slaughter method.The type of pasture and the age of the lambs at weaning had no effect on the efficiency of utilisation of metabolisable energy. The maintenance requirement was 168.0 kcal/kg o.75 24 hr. The efficiency of utilisation of metabolisable energy was 53.5% for lambs fed below maintenance and 29.1% for lambs fed above maintenance. These results are discussed in relation to other published work with young sheep.