The effect of sour milk as a postmilking teat dip for mastitis prevention in a dairy herd.

In a preliminary in vitro study, the growth of Staphylococcus aureus was totally inhibited during incubation for 24 h at 35 degrees C-37 degrees C in a solution of cooked commercial milk with 1% of uncooked commercial sour milk ("A piimä"). In a subsequent clinical trial, "A piimä" sour milk with 5% glycerol was used as a postmilking teat dip from February to June. Quarterly milk samples were drawn once a month aseptically from 133 cows. Percentages of pathogen positive samples and somatic cell count (SCC) from teats dipped with the sour milk were compared with those dipped with a commercial iodine teat dip and those of undipped controls. During March-June there were fewer isolations of S. aureus (2.09%) and coagulase-negative staphylococci (2.52%) in the sour-milk group than in the control group (3.09% and 4.07%, respectively). In iodine group, there were fewer isolations of S. aureus (0.83%) but more isolations of coagulase-negative staphylococci (5.26%) than in the control group. During the study period, the percentages of bacterial isolates did not differ statistically significantly between treatments, p = 0.291. The percentage of quarters with a SCC over 125,000 at the end of the study was one third lower in the sour-milk group than in the control group (16.67% and 26.23% respectively) but the difference was not statistically significant (p = 0.074). The results indicate that a sour-milk teat-dip preparation can inhibit new intra mammary infections (IMI).