Female sheep of five breeds (Scottish Blackface (B), South Country Cheviot (C), Welsh Mountain (W), Lincoln Longwool (L), and Southdown (S)) were purchased as lambs of 5–6 months old and subsequently kept as a single flock on a grassland farm until they were 4½ years old (Southdowns to 3½ years). The sheep were used in a crossbreeding experiment with up to six breeds of ram.
The sheep were weighed and 8 body parts measured at frequent and regular intervals. The Blackfaces and Southdowns grew, relative to their mature size, a little faster initially than the Cheviots. Mature weights (lb.) were approximately B: 146, C: 145, W: 101, L: 197 and S: 129. The breeds differed in conformation but the order of maturity of the body parts was the same for each breed. Variances for body measurements decreased slightly with increasing age for early-maturing parts and increased a little for later parts. The coefficients of variation decreased slightly with increasing age. Variance in weight increased markedly with age (but not the C.V.) and showed the only large breed differences in variance.
Fleece weight, after the first shearing, was strongly affected by the amount of wool shed prior to shearing. Shedding differed significantly between the breeds, Cheviots shedding most. Shedding was also related to the number of lambs born per ewe. The total weights (lb.) of wool produced from four shearings were B: 23·2, C: 20·0, W: 15·6, L: 55·5 and S (estimated from 3 shearings): 20·8.
The numbers of lambs born per ewe totalled over three lamb crops were B: 5·81, C: 5·21, W: 4·53, L: 4·85 and S (estimated from two crops): 4·55. In survival to weaning, single-born lambs were no better than twins and crossbred lambs no better than purebred. Lambs born to Welsh mothers had the best survival; the other breeds did not differ significantly from each other. The breeds of ewe differed in the proportions of their twin lambs which had to be assisted at, or soon after, birth.
When each breed of ewe was mated to the same breeds of ram, the weights of lambs born to Blackface mothers did not differ significantly at birth from those of lambs born to Cheviots but were heavier at weaning. Lambs from Welsh mothers were the lightest at birth and weaning.
In relation to (live-weight)0·73 the maternal performance of the Welsh females was at least as good as that of the Blackfaces but the wool production was slightly poorer.