Personality and production: nervous cows produce less milk.

The objective of this study was to investigate relationships between animal personality (i.e., consistency in behavioral responses, also called temperament) and milk production in dairy cows. There has recently been a growing research interest in animal personality, which in production animals can have an important impact on welfare and production potential. Despite this, the relationship between personality and milk production in dairy cows remains unclear. Here we investigate links between behavioral responses during milking and in personality tests (responses to novel object and social isolation) with milk production in 2 breeds of dairy cattle, Swedish Red and White and Holstein. The milk production parameters investigated were energy-corrected milk (in kg) for the cows' first lactation and energy-corrected milk for their current lactation. Overall, cows that stepped more during milking or spent more time facing the herd during social isolation produced less milk in their first lactation. Cows that vocalized more during isolation had a lower current milk production. Variation in other behavioral responses showed limited relationships with milk production. Taken together, our results support a relationship between behavioral responses and milk production, where cows showing signs of nervousness produce less milk. However, observed relationships are dependent on the milk measure used, behavior, and breed investigated, supporting that the relationship between behavior and production traits is not straightforward.