Risk factors for clinical mastitis, ketosis, and pneumonia in dairy cattle on organic and small conventional farms in the United States.

The US regulations for production of organic milk include a strict prohibition against the use of antimicrobials and other synthetic substances. The effect of these regulations on dairy animal health has not been previously reported. The objective of this study was to characterize disease detection and identify risk factors for selected diseases on organic (ORG) and similarly sized conventional (CON) farms. Dairy herds (n=292) were enrolled across 3 states (New York, Oregon, Wisconsin) with CON herds matched to ORG herds based on location and herd size. During a single herd visit, information was collected about herd management practices and animal disease occurring in the previous 60 d, and paperwork was left for recording disease occurrences during 60 d after the visit. For analysis, CON herds were further divided into grazing and nongrazing. Poisson regression models were used to assess risk factors for rate of farmer-identified and recorded cases of clinical mastitis, ketosis, and pneumonia. An increased rate of farmer-identified and recorded cases of clinical mastitis was associated with use of CON management, use of forestripping, presence of contagious pathogens in the bulk tank culture, proactive detection of mastitis in postpartum cows, and stall barn housing. An increased rate of farmer-identified and recorded cases of ketosis was associated with having a more sensitive definition of ketosis, using stall barn housing, and feeding a greater amount of concentrates. An increased rate of farmer-identified and recorded cases of pneumonia was associated with a lack of grazing, small or medium herd size, and Jersey as the predominant breed. Overall, disease definitions and perceptions were similar among grazing systems and were associated with the rate of farmer-identified and recorded cases of disease.