Genetic correlations of clinical mastitis and feet and legs problems with milk yield and type traits in Dutch Black and White dairy cattle.

Direct selection for decreased disease incidence is difficult given low hsuperscript 2s and the absence of disease recording. Genetic correlations between diseases and type traits indicate possibilities for indirect selection; however, correlations often include experimentally instead of routinely scored type traits. The aim of this study was to estimate genetic correlations of clinical mastitis and feet and legs problems with milk yield and routinely scored type traits in Dutch Black and White [DBW; Dutch Black Pied] cows. From 1983 to 1991, the incidence of diseases was recorded at 44 farms with DBW dairy cattle. Records on 3617 cows sired by 224 bulls were analysed. Heritabilities for milk yield, type traits and diseases were obtained using an equal design multivariate Restricted Maximum Likelihood procedure considering all observations on a continuous scale. A bivariate threshold procedure was used to estimate hsuperscript 2s of diseases and genetic correlations of diseases with milk yield and type traits. Genetic correlations of clinical mastitis and feet and legs problems with milk yield were 0.16 and 0.26 respectively, and hsuperscript 2s for diseases were low 0.01-0.11. Unexpected positive relations between udder type traits and clinical mastitis were found (0.09-0.26), and possible reasons are discussed. Genetic correlations between type traits for feet and legs and problems of the feet and legs were negative -0.01 and -0.24 respectively. Final score for feet and legs could be used as a selection criterion to select to reduce the incidence of feet and legs problems