The Impact of free-stall housing on somatic cell counts in bulk tank milk

Abstract

Dairy housing is generally regarded as a major risk factor for environmental mastitis. Weekly somatic cell counts (SCC) spanning more than a 3 year period were analysed from herds located in the central San Joaquin Valley of California to determine the impact of free-stall housing on somatic cell counts in bulk-tank milk compared with conventional dry-lot housing. Herds with evidence of contagious mastitis pathogens were excluded from analysis. Weather data for daily rainfall and temperatures were also collected. All herd groups had mean SCC less than 300,000 cells/ml. During winter months when most rainfall occurred, herds with open dry-lot housing had a significant increase in SCC that averaged 34?000 cells/ml more than herds with free-stall housing. Although some differences were observed in the summer, SCC were not significantly different between herds with respect to housing type. Economic impacts upon milk production related to SCC changes were estimated to provide a seasonal benefit of $10.25 per cow per winter. The present value of this benefit alone over a 20-year planning horizon would potentially account for 36% of the additional investment cost for free-stall housing.