Field Evaluation of Staphylococcus aureus Bacterin Use in Dairy Farms

A total of 420 lactating Holstein cows in three dairy farms in Damietta (farm A, 120 lactating cows and farm C, 160 lactating cows) and El-Sharkia (farm B, 140 lactating cows) Governorates; were examined for the presence of clinical and subclinical mastitis among the resident cows, then were vaccinated by Staph. aureus bacterin and then were observed during the period from May 2015 to December 2017 for evaluating the efficacy of the vaccine in reducing the number of infected animals and preventing new infections. Clinical mastitis and subclinical mastitis were respectively reported in 286 (17.54%) and 726 (44.53%) out of the total examined quarters (n=1630) from 420 animals in 3 farms. Before vaccination, the overall prevalence rate of Staph. aureus was (19.5% versus 46.5%) in mastitic quarters and (32.1% versus 44.6%)in subclinical mastitis. Vaccination of cows with 5 ml of Staph. aureus bacterin 2 doses with 14-day interval decrease the severity of mastitis in the new cases of clinical mastitis and reduce the prevalence of Staph. aureus and coagulase-negative staphylococcal mastitis, improved clearance rates of existing Staph. aureus mastitis, but it has little effect on reducing new mastitic cases. However, it was found to be effective in preventing new infections with Staph. aureus and coagulase-negative staphylococci in dairy heifers, and minimizing somatic cell count, and increasing milk yield. Also, the total bacterial count, total Staphylococcal count, and Staph. aureus count was reduced. Vaccine efficacy was stretched to fat, protein percent and milk yield were elevated.