The Relationships Between Two Types of Social Networks and the Milk Production of Dairy Cows Maintained With an Automatic Milking System

To investigate what affected the social connections among dairy cows, we conducted social network analyses (SNAs) based on our observations of (i) the social networks (SNW) of dairy cows that visited an automatic milking system (AMS) within the 15-min period from before to after another cow visited the AMS to be milked and (ii) the SNW of formations of pairs of dairy cows lying in adjacent stalls in a free-stall barn. We compared the structures of the AMS SNW and Stall SNW and the relationship of the degree centrality of the cows in the two SNWs with the cows' milk production. The cows' degree centrality within each SNW was significantly and positively correlated with their milk yield, but those in the two SNWs were not correlated with each other, indicating the positions of individual cows differed between the two SNWs. The quadratic assignment procedure (QAP) test revealed a significant correlation of the AMS and Stall SNWs (p < 0.01) in total period, which suggests affirmative relationships between cows might be a common element to connect the same pairs in the two SNWs. The cows' milk yield might have restricted changes in the time intervals of the cows' AMS visits and pair formation.