Abstract
The main factors affecting the outcome of Trueperella pyogenes (T. pyogenes) mastitis were examined through a survey of diagnostic data and interviews relating to the occurrence of T. pyogenes mastitis in 83 quarters from 82 Holstein cows between August 2012 and April 2014. Ultimately, one cow was sold during the examination, and 82 quarters from 81 cows were used for analysis on prognosis. T. pyogenes mastitis occurred year round in both lactating and dry cows. The incidence of T. pyogenes mastitis did not significantly differ by month or show seasonality in either lactating or dry cows. Therefore, the occurrence of T. pyogenes mastitis also differed from that of summer mastitis. The 1-month survival rate of infected cows was 64.6% (53/82), and the recovery rate of quarters with T. pyogenes mastitis was 14.6% (12/82). Bivariate logistic regression analysis was performed with survival and culling of infected cows as objective variables and with recovery and non-recovery of quarters with T. pyogenes mastitis as objective variables. The severe cases were significantly culled (odds ratio, 16.30) compared to mild cases, and the status of quarters didn't recover (odds ratio, 6.50). The results suggest that mild to moderate symptom severity at the time of onset are the main factors affecting outcomes in cows and recovery of quarters infected with T. pyogenes mastitis. Further, high level of NAGase activity also suggested the potential use as an indicator of culling of cows with T. pyogenes mastitis.