Genetic parameters for birth difficulty, lamb vigour and lamb suckling ability in Suffolk sheep

This study investigates the genetic basis of lamb vigour (defined as neonatal lamb activity and sucking ability) and lambing difficulty as potential traits to be included in selection programmes to improve ewe and lamb welfare. Scores for lamb birth difficulty, vigour and sucking ability were collected shortly after birth on 1,520 lambs born in 2006 in 19 different flocks that were members of the UK Suffolk Sire Referencing Scheme. Scores evaluated each trait on a scale of 1 to 4; 1 being no assistance given either during birth or to suck, or excellent vigour, through to 4 where a large degree of assistance was required, or poor vigour. Genetic parameters (heritabilities, genetic correlations) were estimated by fitting an individual animal model using ASREML. Variance components obtained from univariate and bivariate analyses were averaged to provide genetic parameter estimates. Heritabilities for birth difficulty and vigour were moderate but heritability for sucking ability was not significant. The genetic correlation between vigour and sucking ability was positive and high, that between vigour and birth difficulty moderately negative, and that between birth difficulty and sucking ability not significant. Birth difficulty and vigour could be included in Suffolk breeding programmes to help reduce health and welfare problems associated with these traits in Suffolk sheep, and in flocks producing crossbred lambs sired by Suffolk rams. Further work is required to evaluate correlations between these traits and performance traits and to comprehensively validate the scoring system once more data become available.