Udder-related risk factors for clinical mastitis in dairy cows

A cross-sectional longitudinal survey was carried out between February 2009 and January 2010 to evaluate udder-related risk factors for clinical mastitis occurring in dairy herds. Data were used from three dairy farms. Research was divided into four calendar seasons. Cows with clinical mastitis were detected by clinical examination of the udder and determination of abnormalities in milk. Udder level variables, conformation characteristics of udder and teats and teat end to fl oor distances were included in the logistic regression analysis. The estimated incidence risk for CM in the population of dairy cows observed was 85.02 cases per 100 cow�years at risk. The relative risk of CM was lower for primiparous cows, and increased with further parity. The median number of days in milk at diagnosis was 108 days, ranging from a median of 55 to 150 days in lactation. The rear udder quarters had a higher risk of CM incidence compared to the front udder quarters. A Chi square test revealed that farm management and cow parity were signifi cantly connected with incidence of clinical mastitis. Spring was the season with the highest percentage of diagnosed cases of CM, with the exception of farm A, where Fall was the season with the highest percentage of cases. All udder level factors entered in the models were signifi cantly linked with the occurrence of CM. The odds ratio of CM increased signifi cantly as udder morphology worsened, teat ends were fl at and the distance from teat ends to fl oor decreased. It was concluded that conformation udder traits could be used for the genetic selection of dairy cows for mastitis resistance. Key words: dairy cows, clinical mastitis, risk factors