Management practices associated with the incidence rate of clinical mastitis

Risk factors for the incidence rate of clinical mastitis were studied in 27 4 Dutch dairy herds. Variables that were associated with resistance to dise ase were the feeding, housing, and milking machine factors. Variables that were associated with exposure were grazing, combined housing of dry cows an d heifers, and calving area hygiene. Postmilking teat disinfection in herds with a low bulk milk somatic cell count and years of practicing dry cow th erapy were positively associated with the incidence rate of clinical mastit is. Herds with a low bulk milk somatic cell count and in which postmilking teat disinfection was not used had lower incidence rates of clinical mastit is than did other herds. The incidence rate of clinical mastitis caused by Escherichia coli was most ly related to housing conditions, hygiene, and machine milking. The inciden ce rate of clinical mastitis caused by Staphylococcus aureus was mostly rel ated to factors associated with bulk milk somatic cell count and factors th at might be due to cause and effect reversal. A strong positive correlation existed between the incidence rate of clinical mastitis caused by Streptoc occus dysgalactiae and the incidence rate of clinical mastitis caused by St aph. aureus. The incidence rate of clinical mastitis caused by Streptococcu s dysgalactiae was related to nutrition, milking technique, and machine mil king. The incidence rate of clinical mastitis caused by Streptococcus uberi s was associated with factors related to housing, nutrition, and machine mi lking.