In a cross-sectional study, we investigated the effects of human-animal interactions and management factors on udder health in 46 Swiss dairy herds living in loose-housing systems on farms that participated in the Swiss dairy farm network “pro-Q.” The human-animal relationship was measured by observing milkers´ behavior, cows’ behavior during milking, and cows’ avoidance distance in the barn. Management factors were assessed by questionnaire-guided interviews and observations. Udder health was evaluated using indicators that were calculated from milk recording data over a period of 1 yr before assessment: (1) average somatic cell scores (SCS) per herd and (2) incidence of new infections per herd (NEWINF); and indicators that were calculated from quarter milk samples of all lactating cows at the time of assessment: (3) prevalence of quarters with elevated somatic cell counts (>100,000 cells/ mL; %Q>100) and (4) prevalence of mastitis quarters (>100,000 cells/mL and culturally positive; %Qmast). After univariate preselection of associated factors, multivariable linear regression models were calculated at the herd level and a multilevel regression model was calculated at the herd and cow levels for SCS. Among all of the human-animal relationship factors, the most dominant predictor for SCS, %Q>100, and %Qmast was the percentage of positive interactions of milkers with the cows in relation to all of their interactions during milking. Furthermore, a higher prevalence of fearful cows in the herd (with an avoidance distance >1 m) was associated with a higher %Q>100. In herds with a higher NEWINF, incidents of cows kicking during milking occurred more frequently. Concerning management as well as farm and herd characteristics, the following mastitis risk factors were found: (1) breed, especially Holstein with regard to SCS, NEWINF, and %Qmast; (2) high age in terms of lactation number with regard to SCS and %Qmast; (3) high amount of new infections of a cow over 1 yr with regard to SCS; (4) air-adsorption during application of teat-cups with regard to NEWINF; (5) lack of separation of diseased cows with regard to NEWINF; and (6) ample dimensions of lying places with regard to %Qmast. The results suggest that the human-animal relationship is relevant for udder health, especially for cows’ reactions to infections expressed as somatic cell count levels. Risk of infection itself appears to be mainly influenced by management factors. Hence, the human-animal relationship may be considered in extension concerning preventive mastitis control.
