The Effects of Energy Intake During late Pregnancy on Lamb Birth Weights and Lactation of Nigerian Dwarf Sheep

EIGHTEEN Nigerian Dwarf ewe lambs about eight months of age and weighing between 15 and 20 kg were divided into three groups, A, B, and C, and fed diets supplying 75, 100 and 125% of the ARC energy standards (1965) from the 15th week of pregnancy through lactation. Mean daily intakes during the last seven weeks of pregnancy were: dry matter 569, 748 and 826g: digestible organic matter 260, 496 and 593; and calculated metabolizable energy 0.99, 1.81 and 2.16 Mcal for groups A, B and respectively. The daily intakes during lactation were: 660, 748 and 857g of dry matter; 287, 593 and 690g of digestible organic matter and 1.05, 2.16 and 2.51 Mcal of calculated metabolizable energy for groups A, B and C respectively. Mean daily liveweight gains during the last seven weeks of pregnancy were 14.2, 99.0 and 90.0g and during lactation — 43.0, 7.9 and 10.4g for groups A, B and respectively, the differences being highly significant (P <0.01). Mean birth weights of lambs were 1.18, 1.78 and 1.82kg for groups A, B and C respectively, the differences not being significant. Weight gains of lambs were highly significantly correlated with milk yield of their ewes. During a 10-week lactation period the differences in milk yields were highly significant between groups, with average daily yields of 312, 480 and 533g, for A, B and respectively. Peak yields were 481, 697 and 670 g for the respective groups between the second and third weeks of lactation. The mean values for milk composition were: fat, which remained relatively constant throughout lactation, 6.00, 6.36 and 6.40%; protein 4.82, 5.63 and 5.78%; lactose 4.15, 4.30 and 4.34%; total solids, which showed no definite trends during lactation, 15.98, 16.88 and 16.95%; and gross energy, which decreased with advancing lactation, 6.12, 6.18 and 6.38kcal/g for groups A, B and C respectively, the differences not being significant.