Automatic milking systems as a risk factor for intramammary infections caused by environmental pathogens.
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Intramammary infections (IMI) in cows are of great economic impact for the dairy industry. With the increasing number of automatic milking systems (AMS) on dairy farms, it is important to know whether AMS can influence IMI status of the cow. In this study, prevalence of IMI caused by environmental and contagious pathogens were compared between herds with AMS and conventional milking systems (CMS). Milk sample data was collected from 966 cows in 84 Dutch dairy farms; 248 cows were milked by an AMS and 718 cows were milked conventionally. The quarter milk samples were taken at two moments; at drying off and two weeks (+/- 7 days) after calving. Information on management was obtained by means of a questionnaire. Bacteriological culture was performed on the milk samples and the major mastitis-causing pathogens were divided in environmental pathogens (S. uberis, S. dysgalactiae, E. Coli, Klebsiella) and contagious pathogens (S. aureus, S. agalactiae and S. dysgalactiae). Influence of management factors as possible confounders on the relationship between milking system and IMI were statistically analysed through a univariable and multivariable model. A significant association was found between AMS and the occurrence of IMI caused by environmental mastitis-causing pathogens (p<0.05). Parity showed to be a confounder; multiparous cows were more at risk than heifers. For contagious pathogens, no significant relation was shown. This study demonstrated that AMS milked cows are at higher risk of IMI caused by environmental pathogens.