Abstract

The objective of this study was to determine the effects of plane of nutrition during early and mid-pregnancy on the performance of mature ewes and their offspring. From day 0 to day 39 post mating (early pregnancy, EP), 82 multiparous ewes were fed to provide either 60% (low, L), 100% (medium, M) or 200% (high, H) of predicted metabolisable energy (ME) requirements for maintenance, following a synchronised mating. From day 40 to day 90 (mid-pregnancy, MP), ewes were provided with either 80% (M) or 140% (H) of ME requirements. After 90 days of gestation, all ewes were fed to meet requirements for late pregnancy. During EP, mean live weight (LW) and body condition score (BCS) change of ewes were -6.3, -0.8 and +6.0kg and -0.02, +0.10 and +0.22 units in the L-, M- and H-EP treatments, respectively. During MP, mean LW and BCS change were -0.8 and +4.9kg and -0.09 and +0.09 units in the M- and H-MP treatments, respectively (P 0. 00 1). Treatments had no effect (P > 0. 05) on conception rate, although there tended to be an inverse relationship (P = 0.085) between plane of nutrition in EP and plasma progesterone concentrations at day 42 of gestation. EP nutrition influenced foetal development with lambs from ewes offered diet L-EP being smaller (P 0. 01) at day 56 than M- or H-EP lambs. However, at parturition L-EP lambs were heavier (P 0. 05) and tended to have higher (P = 0. 056) immunoglobulin status 24 h after birth. Mortality rates at weaning were reduced (P 0.05) for lambs born from ewes offered diet L-EP compared with M- or H-EP lambs. Diet M during mid-pregnancy resulted in larger (P 0. 05) foetuses at day 80 of gestation. At parturition, these lambs had longer head and crown-rump lengths than H-MP lambs (P 0. 05). Lambs born to ewes offered diet M-MP tended to progress faster to attempting to suckle than H-MP lambs (P = 0.089). There was an interaction between plane of nutrition in early and mid-pregnancy, whereby the highest number of lambs weaned was a result of diet L-EP followed by diet M-MP These results indicate that in adult ewes, temporary nutrient restriction during early pregnancy results in better lamb survival; and mild nutrient restriction in mid-pregnancy tends to improve neonatal behaviour and results in lambs with longer skeletal size.