Low somatic cell count: a risk factor for subsequent clinical mastitis in a dairy herd

A case-control study was conducted to evaluate factors measured at the udde r inflammation-free state as risk factors for subsequent clinical mastitis. The factors including somatic cell count (SCC), body condition score, milk yield, percentages of milk fat and milk protein, and diseases were evaluat ed for their association with the results of udder inflammatory response. T he results of the response were specified as presence (case) and absence (c ontrol) of clinical signs of mastitis. Data on Holstein Friesian cows calvi ng from January 1984 to November 1996 from a commercial farm with low bulk milk SCC were used. Univariable and multivariable random-effect logistic mo dels were used to evaluate the effect of those factors on the risk of clini cal mastitis. The following variables were associated with increased odds o f case versus control events in the univariable analysis: early lactation p eriod, low SCC, high milk yield, high percentage of milk protein, high perc entage of milk fat, low body condition score, retained placenta, and milk f ever. For the final multivariable model of all variables used for analysis, only low SCC remained significantly associated with increased risk of subs equent clinical mastitis. The authors concluded that very low SCC during th e udder inflammation-free state are associated with increased risk of clini cal mastitis.