Dairy herd life in relation to linear type traits and production 1. Phenotypic and genetic analyses in pedigree type classified herds

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Abstract
The relation between survival to complete lactations 2, 3 and 4 and both linear type and production traits of pedigree Holstein-Friesian dairy cattle in the United Kingdom was analysed. There were records on 23 071 pedigree animals which were themselves type classified as heifers. The linear and quadratic phenotypic regressions of survival on most type traits were significant, even with yield fitted as a covariate. Phenotypic regressions of survival on milk, fat and protein yield were significantly positive, but that on protein content significantly negative. Phenotypic correlations with survival were under 0·1 for the linear traits, 0·16 for a subjective total type score, and 0·14 for milk yield. Genetic correlations between survival and type traits, estimated by multivariate restricted maximum likelihood, were as high as 0·4 for several traits of the udder and teats and for total score, and higher than for milk yield or composition. Regressions of survival on estimated sire transmitting abilities gave rather lower estimates of genetic correlations, except for total score. The results indicate that in these pedigree and classifying herds the total score is a culling criterion in its own right.