This study evaluated the effect of a Staphylococcus aureus
bacterin and
nisin on bovine subclinical
mastitis. A total of 75 Holstein subclinically mastitic cows were randomly allocated to three groups with 25 cows per group. In group I, an intramammary infusion of
nisin Z at a dose of 2.50×106 IU was carried out once daily for three days, and an autogenous S. aureus
bacterin was inoculated into the supramammary lymph node one week before and one week after
nisin treatment. In group II,
nisin was administered in the same way as in group I, but no
bacterin was inoculated. Group III received no treatment and served as a control. Milk was aseptically sampled from the affected quarters before and 2, 4, and 6 weeks
after treatment, for bacteriological examination and analyses of N-acetyl-β-D-
glucosaminidase (
NAGase) activity, somatic cell count (SCC), and
milk protein and fat contents. Results indicated that, compared to the
nisin-treated group,
nisin-
bacterin treatment significantly reduced intramammary S. aureus
infections, reduced the number of quarters with milk SCCs of more than 5×105 cells/ml, and increased the
protein and fat contents of the milk. Therefore,
nisin-
bacterin therapy is suggested when subclinical
mastitis occurs in lactating cows.