Management practices associated with the bulk-milk prevalence of Staphylococcus aureus in Canadian dairy farms.

When designing mastitis-prevention and control programs, it is important to know the level of adoption of mastitis-prevention management practices and control programs and the herd-level prevalence of contagious mastitis pathogens. Our objectives were to estimate: (1) adoption of recommended mastitis-preventive management on Canadian dairy farms; (2) herd-level prevalence of contagious mastitis pathogens on Canadian dairy farms; and (3) associations of certain management practices with the isolation of Staphylococcus aureus from the bulk tank milk from Canadian dairy farms. In total, 226 farms participating in dairy herd improvement milk recording were randomly selected. All participating farms in British Columbia had free-stall barns and 85% of farms in Québec had tie-stall barns. Post-milking teat disinfection was practised on 96% of the farms and 72% had implemented blanket dry-cow treatment. Weighted and province-stratified prevalence of Streptococcus agalactiae and Staph. aureus in bulk tank milk was 4% (95% confidence interval: 0-12%) and 74% (95% confidence interval: 61-86%), respectively. Highest Staph. aureus prevalence was found in Nova Scotia (91%) and lowest prevalence in British Columbia (38%). No Mycoplasma spp. were isolated, but detection of Mycoplasma spp. could have been hampered by the frozen shipment and storage of the milk samples. Management practices associated with a lower probability of isolating Staph. aureus were blanket dry-cow treatment and believing that a nutritionist is important in mastitis data review. Having the milking equipment checked by an independent technician at least once a year and rubber mats or mattresses in the free-stall barns were associated with an increased probability of isolating Staph. aureus from the bulk tank. Most of Canadian dairy farms adopted important mastitis-prevention practices, such as post-milking teat disinfection and drying off all cows with antibiotics; however, improvements can still be made. A few management practices were associated with the prevalence of Staph. aureus in bulk tank milk, such as dry-cow treatment and barn type for the lactating cows. Further work has to be carried out to investigate to what extent the associations are causal.

Prevalence of contagious mastitis pathogens in bulk tank milk in Prince Edward Island.

The purpose of this study was to 1) estimate the herd prevalence of contagious mastitis pathogens in bulk milk from Prince Edward Island (PEI) dairy farms, 2) determine the association between bulk milk culture results and mean bulk milk somatic cell count (BMSCC), and 3) investigate the agreement of repeated bulk milk cultures. Three consecutive bulk milk samples were obtained at weekly intervals from all 258 PEI dairy herds and were cultured using routine laboratory methods. Cumulative prevalence of Staphylococcus aureus, Streptococcus agalactiae, and Mycoplasma spp. (M. bovis and M. alkalescens) was 74%, 1.6%, and 1.9%, respectively. Bulk milk somatic cell count of Staph. aureus-positive herds was higher than that of negative herds. Agreement for Staph. aureus isolation between 3 consecutive tests was moderate (kappa = 0.46). Mycoplasma bovis and M. alkalescens in bulk milk are being reported for the 1st time in PEI ever and in Canada since 1972.