Differences in lamb production between ewe lambs and mature ewes

Currently, comparisons of lamb output from either ewe lambs or mature ewes are confounded, as the age groups are bred to different sires, and lamb at different times. The aim of this experiment was to compare the reproductive performance of ewe lambs and mature ewes, bred at the same time to the same sires, and lambed in the same climatic conditions. The experiment included 1082 mature ewes and 1014 ewe lambs that gave birth to 2656 lambs. Birth weights of lambs were 3.92 ± 0.06 kg and 5.02 ± 0.06 kg, and weaning weights of lambs were 24.03 ± 0.24 kg and 26.68 ± 0.29 kg for ewe lambs and mature ewes, respectively. Lambs born to ewe lambs were less vigorous than lambs born to mature ewes, even when adjusted for their lighter birth weights. Lamb survival during the neonatal period was 92.2% and 97.3% for lambs born to ewe lambs or mature ewes, respectively. The effect of birth weight on survival within each dam age and lamb birth rank followed a quadratic form, and differed for each group. Farmers should preferentially allocate all ewe lambs and mature ewes bearing triplets to lamb in paddocks that provide better conditions for lambing.