Impact of pasture allowance during the transition period in ewes carrying singles, twins and triplets on lamb survival, growth and ewe efficiency to weaning with and without human intervention

Abstract

Ewe and lamb mortality increases with fecundity, but practical on-farm solutions remain limited. This study evaluated the effects of pasture allowance during the transition period, from 100 days of gestation to 4 weeks of lactation, and its interaction with litter size on ewe and lamb performance with and without human intervention. The design was a 2 × 3 factorial, with two pasture allowances — High and Std, (achieved through pasture allocation regimes of 3000/2000 kg DM/ha and 2000/1400 kg DM/ha pre-/post-grazing for High and Standard respectively) — and three litter-size classes:
single, twin, and triplet. Allowances were calculated for twin-bearing ewes and applied to all ewes regardless of litter size. Ewe body condition score was similar between all groups until late gestation, decreased from late gestation to 4 weeks of lactation as litter size increased, but were stable thereafter. These results highlight the mismatch between feed consumed and the energetic demands of late pregnancy and early lactation as litter size increases. Increasing pasture allowance
reduced ewe mortality and morbidity and improved ewe efficiency by increasing survival of triplet-born lambs with intervention and twin- and triplet-born lambs without intervention. First-year data suggest current New Zealand pasture allowance recommendations may limit performance of highly fecund ewes, although further research is needed to confirm mechanisms, practicality, and economics.