Effect of live weight at joining on birth weight and weaning weight of lambs

Live weight of ewe lambs at joining has a linear and positive impact on birth weight and weaning weights for both Merino and Composite ewes.

For Merino ewes, birth weight of twin lambs improved by nearly 0.5kg to 4.5kg, if live weight at joining was 55kg rather than 35kg.

Single lambs preformed similarly but the weight increase was from approximately 4.8kg to 5.2kg for the same live weight increase.

At weaning, twin lambs increased from less than 18kg to over 20kg and single lambs increased from 22kg to over 24kg.

Joining weights of composite ewe lambs shows the same trend, but the response in birth weight is stronger for multiple born lambs than for singles.

Increasing ewe joining weight from 30kg to 60kg increased birth weight from 3.1kg to over 4kg for triplet born lambs, but the same joining weight increase only improved single lamb birth weight from approximately 4.7kg to just over 5kg.

Weaning weights of lambs from Composite ewe lambs increased similarly for singles, twins and triplets at the same change in joining live weight, increasing from 20kg to 28kg for triplet born lambs and from 27.5kg to 35kg for singles.