The effect of neighbouring cows within the milking parlour on a cow's daily milk yield

Social interactions in a dairy herd are essential to maintain the herd's structure. Disturbances in social relationships can be stressful and may impact both animal welfare and production. Pathological and physiological changes, biological variations, but also the social environment induced by surrounding cows can affect variation in the daily milk production. This study aims to investigate the social interplay between cows during milking by examining the milking order in a milking parlour and determining if the individuals a cow stands next to will affect its daily milk yield. Milking order data from 234 individuals was collected from a two-sided herringbone parlour twice a day for 35 days. The indirect effect of the neighbour cows in the milking parlour was studied by fitting a linear mixed model to the daily milk yield residuals. The estimated indirect effects on milk yield ranged from -1.07 kg to 0.85 kg. We described a weak negative correlation of -0.26 (SE: 0.09) between direct and indirect effect estimates. The average of the indirect effects of neighbouring cows differed between different lactation stages and regrouped cows changed to a more negative estimated indirect effect in their new group. Our results show individual variation in the average indirect effect on the milk yield of the neighbour, with some individuals having a positive effect on their group mates, while others have a more negative effect. Further investigation of these effects would be helpful in selecting the best individuals in a herd and optimising group composition and milking routines.