Supplemental material for: Post-partum mood states of dairy cows: effects of separation from the calf and consistency over time

The grain reward was then reduced to 0.1 kg/trial for 5 sessions. During the first SNC test, cows kept with their calf for 3 days were slower to reach the initial reward after separation than control cows. Following the reward reduction, approach latencies increased for both treatments, but cow-calf contact cows were more likely to exhibit slow approaches, indicating stronger response to the loss of reward.

At one month post-calving, cow-calf contact cows remained more likely to show slow approaches to the reduced reward than control cows. Individual responses to reward loss were positively correlated across tests, suggesting individual consistency in responses to reward loss over time. Overall, cows that remained with their calf for 3 d showed lower reward sensitivity and stronger responses to reward loss than control cows, consistent with anhedonia-like responses and more negative mood states.

These effects persisted for up to one month post-calving, and, together with the observed individual consistency over time, suggest that early post-partum stressors may have lasting effects on dairy cows’ mood states.