The influences of live weight and body condition score of ewe lambs from breeding to lambing on the live weight of their singleton lambs to weaning

One of the limiting factors to the adoption of breeding 7-month-old ewes is that their lambs are lighter at birth and weaning than lambs born to mature ewes. The present study tested the hypothesis that the live weight and body condition score of 7-month-old ewes at breeding and during pregnancy would influence the live weight of their singleton-born lambs to weaning. Data was collected on one commercial sheep farm from 591 ewes across two years. In 2011 and 2012, during pregnancy the ewes gained 14.6 and 10.1 kg of total live weight, respectively. Multiple regression analysis indicated that live weight of ewes at breeding had a positive effect (P < 0.05, 0.03 ± 0.02 kg of birth weight per kg of ewe live weight) on lamb birth weight while ewe live weight in late pregnancy had a negative effect (P < 0.05, −0.03 ± 0.01 kg of birth weight per kg of ewe live weight). Overall the R-square of the model for lamb birth weight was small (R2 = 0.01) indicating, that live weight of the ewe was not a major contributor to the live weight of lambs at birth. The live weight of ewes in late pregnancy had a positive impact on both the live weight of lambs at approximately 18 days of age and at weaning (P < 0.05, 0.05 ± 0.02 and 0.08 ± 0.03 kg of lamb live weight per kg of ewe live weight, respectively) but again the R2 value for the multiple regression was small (0.01). Body condition score of the ewe at breeding and in mid-pregnancy had no effect (P > 0.05) on lamb birth weight. In contrast ewes with body conditions scores of 3.5 and 4.0 or greater in late pregnancy gave birth to lighter lambs (4.9 ± 0.1 and 4.7 ± 0.2 kg, respectively) than ewes with body condition scores of 2.5 or less (5.3 ± 0.1 kg) or 3.0 (5.2 ± 0.1 kg, P < 0.05). There was no effect (P > 0.05) of ewe body condition score on lamb live weight at approximately 18 days of age or at weaning. Therefore, under the conditions of this study ewe live weight and condition score during pregnancy had a minimal effect of lamb live weight from birth to weaning.