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 lo w heritabilities and absence of disease recording. Genetic correlation s between diseases and type traits indicate possibilities for indirect selection; however, correlations often include experimentally instead stead of routinely scored type traits. The aim of this study was to e stimate genetic correlations of clinical mastitis and feet and legs pr oblems with milk yield and routinely scored type traits in Dutch Black and White cows. From 1983 to 1991, incidence of diseases was recorded at 44 farms with Dutch Black and White dairy cattle. In total, record s on 3617 cows sired by 224 bulls were analyzed. Heritabilities for mi lk yield, type traits, and diseases were obtained using an equal desig n multi-variate REML procedure considering all observations on a conti nuous scale. A bivariate threshold procedure was used to estimate heri tabilities for 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 unfavorable (0.16, 0.26), and heritabilities for diseases were low (0.01-0.11). Unexpected posit ive relations between udder type traits and clinical mastitis were fou nd (0.09-0.26), and possible reasons were discussed. Genetic correlati ons between type traits for feet and legs and feet and legs problems w ere negative (-0.01, -0.24). Final score for feet and legs might be us ed as selection criteria to select for lower incidence of feet and leg s problems.