RESUMEN
The objective of this cross-sectional, herd-level study was to identify associations between calf management practices and herd-level preweaning mortality on Ontario dairy farms. From April to August 2022, a convenience sample of 100 dairy farms from Ontario, Canada, were visited once. A questionnaire, covering farm biosecurity, calving, colostrum management, preweaning nutrition, and housing, was verbally administered at each farm visit. Furthermore, data regarding preweaning calf mortality were retrieved from each farm's herd management software or records, including the total count of calves that survived, were culled, or died during the preweaning period for the 365 d before the farm visit. Preweaning mortality was defined as the proportion of calves that died between ≥48 h and 60 d of age divided by the total number of calves alive after 48 h of age. The herd-level preweaning mortality risk on sampled farms ranged from 0 to 15.9%, with an average of 2.8% (SD = 3.8%). A multivariable Poisson regression model was used to evaluate associations between 22 explanatory variables and preweaning mortality. Factors associated with greater herd-level preweaning mortality were larger herd size; having treatment protocols for diarrhea, pneumonia or navel infection written in collaboration with a veterinarian (compared with farms with the same treatment protocols developed without a veterinarian), and the herd-veterinarian never inquiring about calf health (compared with farms where the herd veterinarian inquired sometimes). Factors associated with lower herd-level preweaning mortality were using the calving pen for sick cows, having more than 4 people working with calves, offering calves a minimum volume of ≥9 L of milk/day, and farmers with a level of formal education higher than secondary school. These results indicate that producers may be able to reduce preweaning calf mortality by providing adequate labor for calf care, offering calves sufficient volumes of milk, being proactive in communicating with their veterinary practitioners about calf health, and potentially by engaging in continuous education.
RESUMEN
Salmonella Dublin is an emerging pathogen on dairy farms in Canada. In Ontario, Salmonella Dublin has been increasingly isolated from diagnostic laboratory samples. The objective of this observational cross-sectional study was to identify management practices associated with herd positivity for Salmonella Dublin. A convenience sample of 100 dairy farms was visited in Ontario, Canada, from April to August 2022. Farms were visited once to collect blood samples from 20 heifers between 4 and 24 mo old, sample bulk tank milk, and administer an in-person questionnaire on management practices. An additional bulk tank milk sample was collected before the visit by milk transporters. All bulk tank and serum samples underwent ELISA testing to determine Salmonella Dublin positivity (≥35% positivity on ELISA). Of the 1,990 heifers sampled, 44 (2.2%) animals were seropositive for Salmonella Dublin. At least one seropositive heifer was identified on 24% of participating farms. Based on the bulk tank milk samples collected during both sampling periods, 4% of farms were positive for Salmonella Dublin. Overall, of the 100 farms visited, 25% were classified as Salmonella Dublin positive, meaning at least one serum or bulk tank sample was interpreted as positive. A multivariable logistic regression model identified 5 factors associated with herd-level positivity for Salmonella Dublin. Specifically, introducing purchased animals within the last 2 years increased the likelihood that farms were positive for Salmonella Dublin (odds ratio [OR] = 4.6). Farms that had at least one animal leave the premises for a cattle show, embryo collection center, or loan to another farm and return within the last 2 years were also at a higher risk for Salmonella Dublin (OR = 4.9). Farms that removed manure from the surface of bedding in calving pens twice per month or after every calving were at greater risk for Salmonella Dublin than farms that removed manure less frequently (OR = 8.5). Farms that added bedding material to calving areas once or twice weekly were at lower risk for Salmonella Dublin compared with farms that added bedding less than once weekly (OR = 0.1). In addition, farms that kept 3 cows or less per pen in the calving area were at lower risk for Salmonella Dublin. Test positivity for Salmonella Dublin among Ontario dairy farms sampled is high, and dairy producers should consider avoiding management practices that are associated with an increased risk of Salmonella Dublin infection.