Milking vacuum influencing indicators of udder health.

In 23 first-calf heifers we ascertained effects that milking vacuums of 34, 42.5, and 51 kPa had on udder health by percentage of quarter-samples positive for Staphylococcus aureus, total counts of bacteria on blood agar, teat end scores, California Mastitis Test, and direct microscopic somatic cell count. Measures were higher for 51 kPa than for 34 or 42.5 kPA. Samples from cows milked at 42.5 kPa had a lower percentage of samples positive for Staphylococcus aureus, lower total count, lower California Mastitis Test, and lower direct microscopic somatic cell count than samples from cows milked with 34 kPa. Test end scores increased with increase in milking vacuum. Approximately 49% of the samples from cows milked with 51 KPa were positive for Staphylococcus aureus compared with 19.9 and 16.7% for 34 and 42.5 kPa. Milking vacuum of 51 kPa resulted in the highest percentage of cows with three (44.5%) and four (24.1%) quarters positive for Staphylococcus aureus. A milking vacuum of 51 kPa could increase mastitis in a herd having Staphylococcus aureus as the prevalent microorganism causing mastitis.