Farm Table says:
This paper acknowledges that “the single largest influence on the survival of lambs in the first few days of life is their birthweight”. This research looks at the extent to which live weight during pregnancy and lactation of Merino ewes can be used to predict the birth weight and survival of lambs to weaning.
The research was conducted at two sites in 2001 and 2002:
- 700 ewes in Victoria (Hamilton)
- 300 ewes in Western Australia (Kendenup)
Both of these sites have winter-spring predominate rainfall, dry, hot summers, and annual rainfall average of 590mm (Vic.) and 540mm (WA).
The trials found average differences at:
- Day 100 of pregnancy: 7kg in ewe live weight and 0.7 condition score
- Lambing: 11.9 kg and 1.3 of a condition score.
- Average birth weights ranged from 4.0kg to 5.4kg and survival ranged from 68% – 92%, with all lambs deaths to weaning occurring in the first 48 hours.
Additional results included:
- Ewes at CS 2 at day 100 had lighter lambs than those in CS 3
- Lambs from ewes on 800 kg DM/ha during late pregnancy had lower survival rates
- Biggest effect on survival to 48hrs was the birthweight of the lamb
- Higher chill index after 48hr reduced survival of male lambs more than female lambs.
The research confirmed that the birthweight of lambs is significantly related to the live weight of their mother. The researchers stated, “The change in live weight of ewes in late pregnancy had the largest effect on survival, however their live weight at joining and live weight change during the first 100 days of pregnancy were also important”.