Selection for economic characters in Australian Merino sheep. 3. Inheritance of skin-fold score in Merino sheep and problems of scale.

Abstract

A study of published data on the fold scores of certain breed crosses, backcrosses, and filial generations suggests that causes of variation in skinfold score act geometrically. A logarithmic transformation increased the accuracy of prediction of F₂ and backcross scores. Data from selection experiments on Merinos at Trangie were analysed using both arithmetic and logarithmic scales. Heritability of breech fold score was estimated as 0.45 on an arithmetic scale, 0.55 on the logarithmic scale. The mean and variance within groups of Merinos with different means were strongly correlated on the arithmetic scale, but this correlation was removed by the logarithmic transformation, resulting variances being approximately constant. Freedom from folds showed strong potence on both arithmetic and logarithmic scales. Theoretical implications of potence and geometric action appear to be confirmed by available data.