Factors Affecting Condition and Conformation of Crossbred Spring Lambs

Abstract

The differences in condition score between Suffolk-sired and Southdown-sired lambs were not consistent. Similarly, differences in conformation scores were not significant; however, the tendency was for Southdown-sired lambs to be scored higher. Consistent tendencies were for Hampshire-cross and Cheviot-cross lambs to score higher in condition than Border Leicester-cross and Romney-cross lambs, the latter scoring the lowest. Conformation scores displayed similar tendencies among ewe-breeds. The importance of specific sire-breed × ewe breed cross in producing lambs with high condition is apparent, in that Border Leicester-cross ewes produced higher scoring lambs from Southdown sires than from Suffolk sires. Lambs from Hampshire-cross, Cheviot-cross and Romney-cross ewes performed equally well when their lambs were sired by either Southdown or Suffolk rams. The interaction of inherent growth rates from the sire breed with post-natal maternal effect of ewe breed would account for the breed interaction in fattening response of lambs. The residual variation is largely genetically influenced variation by nature of the breeding design. It is partly a response to genetically different pre- and post-natal maternal environments, and partly due to widely segregating genetic differences in the growth pattern among the lambs, and assumed an important role in the determination of condition in lambs. Birth type contributed the greatest comparative effect on condition score of any of the factors studied. Twin lambs scored from 5.22 to 10.26 points lower than single lambs. Conformation scores were significantly different between single and twin lambs. No differences attributable to sex or to the interaction of birth type and sex existed in condition or conformation scores. There was no association between birth weights of lambs and their condition score at weaning. The regression of conformation score on condition score indicated that for each unit increase in condition score a lamb would be scored 0.62 to 1.27 units higher in conformation under the existing scoring system, and that the effects of all other variables on conformation scores were removed by adjusting for condition score. The conformation score assigned to a lamb is thus apparently largely dependent on the condition of the lamb at the time of scoring.