Reducing mob size increases the survival of twin-born Merino lambs when feed-on-offer from pasture is limited and ewes are supplementary fed during lambing

Publication date: Available online 16 February 2019Source: Small Ruminant ResearchAuthor(s): Amy Lockwood, Serina Hancock, Gavin Kearney, Andrew ThompsonAbstractImproving the survival of twin-born lambs is a high priority for the Australian sheep industry. Higher mob sizes at lambing have been suggested to decrease the survival of twin-born lambs. However, our recent work indicated that this effect may not occur when feed-on-offer (FOO) exceeds 2400 kg DM/ha during the lambing period. Increasing mob size at lambing when FOO is limited may exacerbate the risk of mismothering due to the need for ewes to seek feed and thus result in poorer lamb survival. Therefore, this study tested the hypothesis that (i) a higher mob size at lambing will decrease lamb survival when FOO from pasture is limited and ewes are supplementary fed and (ii) that this is related to a greater rate of interaction with foreign ewes and lambs during the periparturient period. Twin-bearing Merino ewes (n = 795) were allocated into one of two treatments on day 140 of pregnancy; high (n = 210) or low (n = 55) mob size, with three replicates of each treatment. Feed-on-offer from live pasture at lambing was below 390 kg DM/ha and ewes were supplementary fed until lamb marking. Behaviour during the periparturient period was observed and dead lambs were collected for autopsy for 14 days during the peak of lambing. The survival of lambs to marking was recorded for each mob. Lamb survival was 6.2% higher...
Source: Small Ruminant Research - Category: Zoology Source Type: research