Health and reproduction in organic and conventional swedish dairy cows

This thesis compares indicators of animal health and reproduction in organically and conventionally managed dairy cows in Sweden. The first part of the thesis is based on data from a twelve-year longitudinal study of a research farm with parallel but separate organic and conventional management. The second part of the thesis is based on data from a field investigation performed by the author. The field investigation included 20 organically and 20 conventionally managed dairy herds in south-east Sweden. Udder health and reproductive performance were studied in both the research farm and in the field study, general health and length of productive life in the research farm only and early-lactation metabolic profiles in the field study only. Udder health was assessed by comparing somatic cell counts during first 150 days in milk, number of test-milking occasions with >200,000 cells/ml during first 150 days in milk and number of veterinary treated cases of mastitis. Reproductive performance was assessed by comparing calving interval, calving-to-first insemination and pregnancy success at first insemination. Body condition score and blood metabolites indicating negative energy balance such as non-esterified fatty acids, beta-hydroxybutyrate, glucose and insulin were measured. Multivariable, multilevel statistical models were consistently employed. Management type, breed, housing, parity, and milk yield were frequently used predictor variables in the different statistical models. The predictor variable of main interest, organic or conventional management, was forced to stay in all models. The conclusion is that under Swedish conditions, cows in organic and conventional dairy management differ only marginally considering mastitis, reproductive performance and metabolic profiles, implying that animal health in organic management is equally good as in conventional management in these specific fields.