Ewe lamb nutrition during pregnancy affects pregnancy outcome

Abstract

This experiment aimed to investigate the impact of pregnancy nutritional treatment on ewe lamb pregnancy rate and pregnancy loss and the liveweight of resulting lambs. Two hundred and forty ewe lambs mated during a 5-day breeding period were randomly allocated to one of three nutritional regimes (‘low’, ‘medium’ and ‘high’). The low (n = 80) treatment group was fed pasture to maintain liveweight during the first 100 days of pregnancy, thereafter feeding was increased to achieve a total liveweight change of 180 g/day. The medium treatment group was fed to ensure a liveweight change equivalent to 100 g/day throughout the entire pregnancy period, while the high treatment group was offered feed ab libitum. The target liveweight changes were achieved in all ewe lamb treatment groups. Fewer (P < 0.05) ewe lambs were scanned pregnant at day 50 of pregnancy and lambed in the high treatment compared with their medium counterparts. In addition, fewer (P < 0.05) low treatment ewe lambs lambed compared with the medium treatment ewe lambs. The lower numbers lambing in the low and high treatment groups were somewhat explained by greater (P < 0.05) pregnancy losses between day 50 and term. Lambs born to low treatment ewe lambs were lighter (P < 0.05) at birth (L0), L53 and L87 and had lower (P < 0.05) survival rates than those born to either medium or high treatment ewe lambs. While the present study was not designed to identify optimal ewe lamb feeding levels in pregnancy, it clearly indicates adverse effects from either a low or high level of pregnancy nutrition beginning in early pregnancy. Therefore, further studies are required to identify the optimal pastoral feeding conditions for the pregnant ewe lamb.