Published online by Cambridge University Press: 02 September 2010
First lactation records for production traits (milk, fat and protein yields) and 17 linear type traits for 7169 Ayrshire heifers were analysed to estimate genetic parameters for type traits and to examine the relationship between type and production traits. A multivariate restricted maximum likelihood procedure fitting a sire model with sire relationships included was used for all analyses.
Heritabilities for production traits were approximately 0·3 and genetic correlations among them were high (>0·84). The estimates of heritabilities for type traits were mainly low to moderate ranging from 0·04 to 0·42. Angularity (0·80), beef shape (0·49), foot angle (0·53) and stature (0·46) had higher heritabilities. Generally phenotypic correlations among type traits were lower than the genetic correlations. The highest negative genetic correlation was between rear legs side and rear legs rear (-0·95) and the highest positive correlation between chest width and beef shape (0·93).
Genetic correlations between type and production were low to moderate and were similar for milk, fat and protein yields. The genetic correlations between the production traits and chest width, udder depth and beef shape were negative but were positive between production and angularity, rear udder width and teat placement side.