IMPACT OF MILKING CHARACTERISTICS AND MORPHOLOGY OF UDDER AND TEATS ON CLINICAL MASTITIS IN FIRST-LACTATION AND 2ND-LACTATION NORWEGIAN CATTLE

Data from the Norwegian progeny testing program were used to examine t he impact of milking characteristics and morphology of udder and teats on clinical mastitis in first- and second-lactation Norwegian cattle. The study was designed as a 1-1 matched case-control study with herd, parity, days in lactation and calving season as matching variables. C onditional maximum likelihood logistic regression was used to evaluate the effects of three primary (2 min milk, milk leakage and teat-end-t o-floor distance) and six other study variables. Treatment records fro m the Norwegian health card system on acute and chronic clinical masti tis were used to define cases. The chosen model included 565 matched p airs. Significant risk factors of clinical mastitis were decreasing te at-end-to-floor distance (P = 0.02) and periparturient udder edema (P < 0.01). Borderline effects were demonstrated by larger than herd-aver age teat diameter (P = 0.04), udder asymmetry (P = 0.05) and increasin g 2 min milk (P = 0.08). Results were compared to a previous study on the same data with log, somatic cell count as the dependent variable. Inclusion of teat-end-to-floor distance in the genetic improvement sch eme may increase the efficiency of genetic selection for mastitis resi stance.