The effect of discontinuation of postmilking teat disinfection in low somatic cell count herds. II. Dynamics of intramammary infections.

Results of a 20 month split-udder trial on the effect of discontinuation of postmilking teat disinfection on intramammary infections (IMI) with major and minor pathogens in seven dairy herds with a low somatic cell count are described. The incidence of Escherichia coli IMI was found to be significantly lower, whereas the incidence of IMI with Staphylococcus aureus and minor pathogens was significantly higher in quarters for which postmilking teat disinfection was discontinued than in disinfected quarters. It was concluded that discontinuation of postmilking teat disinfection decreased the incidence of E. coli IMI, accompanied by a, from a practical point of view, acceptable rise in somatic cell count. However, the possible increase in the incidence of S. aureus IMI calls for careful monitoring of the dynamics of IMI with contagious pathogens, when postmilking teat disinfection is discontinued in an attempt to reduce E. coli mastitis.