Whether a cow is pregnant
affects her behaviour at weaning
D.B. Haley, J.M. Stookey
and J.M. Watts
University of Saskatchewan,
Saskatoon, Canada
Based on anecdotal accounts and theories of parent-offspring conflict and sibling rivalry, we expected that non-pregnant (open) cows would be more averse to abrupt weaning than pregnant cows. We hypothesised that on the days following weaning, open cows would spend more time in proximity to the fence-line which separated them from their calves, vocalise more and spend less time eating. Twenty cows were fence-line weaned from their calves in two repetitions of 10 (5 open, 5 pregnant). Based on real-time ultrasound measurements, gestating cows were assessed to be between 90 and 157 days pregnant. Observers knew that 50% of cows were pregnant but did not know the status of individuals. Cows and calves were observed for 5 days from 0700 to 1700 hours, starting on the day of separation. Using instantaneous sampling at 5 minute intervals we recorded the spatial location of each animal (cows and calves) within their pens, and their activity (lying, standing or walking and if they were eating, ruminating, drinking or otherwise ‘idle’). We also spent 2 minutes at each interval recording which animals vocalised and how often. A repeated measures analysis was used for the statistical model. Overall, open cows spent more of their time in the areas closest to the calf pen (P < 0.05), although there was no difference between open and pregnant cows on day 1. Frequency of vocalisations decreased over the 5-day period but was not influenced by pregnancy status. Cows were most vocal on days 1 and 2. There were no overall treatment differences in the frequency of observations of eating or ruminating, though both groups ruminated less on the day of weaning. The greater time in proximity to the calf shown by open cows, may indicate stronger motivation to continue investment in the current offspring.