Epsilon Open Archive

Abstract

This thesis describes some factors associated with mastitis in Swedish dairy herds, and with udder health of first-parity dairy cows. These factors were investigated in four observational studies including a total of 343 dairy herds and 3315 first-parity cows throughout Sweden. The herds were visited and the farmers interviewed about management, housing, feed, feeding, and milking. The quality of feed, as well as presence of udder pathogens at a case of clinical mastitis, was investigated in two of the studies. Blood samples were taken from first-parity cows in the period two weeks before calving to six weeks after calving for analysis of metabolites and immunological parameters in one of the studies. Udder health measurements used as outcomes in the studies were being a herd with a low or high incidence rate of veterinary treatments of clinical mastitis (CM), being a first-parity cow veterinary treated for CM in the period -7 to 30 days after calving, the within herd number of first-parity cows veterinary treated for CM in the period -10 to 60 days after calving, being a first-parity cow with somatic cell count (SCC) ≥ 200,000 cells/mL at first test-milking, the within herd number of first-parity cows with SCC ≥ 200,000 cells/mL at first test-milking, and as SCC of first-parity cows at first test-milking. Associations between the registered variables and udder health were statistically analyzed using multivariable linear, logistic and Poisson regression models. Results showed that farmer attitude toward treatment of a case of mastitis differed, some contacted a veterinarian at very mild signs of mastitis, while others waited until the cows showed more clinical signs. Moreover, several feed and feeding variables, and hygienic parameters, especially around calving, were found associated with udder health. Furthermore, the results showed that cows of the Swedish Red breed and herds with the majority of cows of this breed, on average have a more beneficial udder health status than cows, or herds with the majority of cows, of the Swedish Holstein breed. Several metabolites and immunologic parameters were associated with SCC at first test-milking, and most of these parameters varied significantly between breed and between first-parity cows of different age at first calving.