Short communication: exploring patterns of variation in conformation data by means of principal components analysis

To explore patterns of variation in Holstein conformation data, 19 genetic correlation matrices from the May 2006 Interbull routine international sire genetic evaluation were reparameterized using an approximate factor analysis. For the udder traits teat length and rear teat placement, only 3 and 5 principal components explained 98 and 99% of the total variation, respectively, whereas 9 to 13 were necessary for overall conformation traits. The absolute deviations of the reparameterized genetic correlations from the initial genetic correlations were lower than 0.03 when 98% of the total variation was considered. The countries with the most frequent large contributions (>0.30) to the second eigenvector for the body, mobility, and overall traits were Australia, New Zealand, Switzerland, Estonia, and Poland. For the udder traits no clear pattern was observed.