click image to zoomAlise SjostromIf calves stay with their mother for days or weeks, the strong bond can result in a bad mood for the calf when broken at 42 days of age. Separating calves from their dam late gives them an attitude similar to dehorning, according to new research from the University of British Columbia (UBC), published last week in the open journal PLOS ONE.
The study noted that calf and dam are separated much earlier than what occurs in nature, usually within hours of birth. But when they’re kept together for days or weeks, the abrupt separation can result in intense behavioral and physiological responses.
In the UBC experiment, 13 bull calves were kept with their dams in a pen for 24 hours after birth. Then, the cow-calf pairs were moved to a pen with other cow-calf pairs that varied from 4 to 8 pairs throughout the experiment. Calves were free to roam throughout the sand-bedded freestalls from 7 p.m. to 7 a.m., but were secluded to a sawdust-bedded “creep” area during the day. In the creep, calves could physically interact with the cows. But, throughout the whole experiment, udder nets prevented calves from suckling.
The calves were trained to associate a white screen with a milk reward, and a red screen with no reward, as they had in a previous dehorning experiment. Calves saw 60 different screens during training, with 23 positive (white) and 22 negative (red) and another 15 that were colors in-between red and white. When calves saw a white screen, they would need to get within 20 centimeters of the screen, then turn around to receive a milk reward.
At 36 days of age, calves were dehorned using a local anesthetic and an intramuscular sedation injection. At 42 days of age, calves were removed from the experimental pen and dams were moved to a new pen in a different barn after milking.
With just an average of 32 training sessions under their belts, the calves could discriminate between positive and negative screens 98 to 99 percent of the time, according to the researchers. But after both dehorning and separation from the dam, calves were less likely to approach the ambiguous screens and receive their milk reward. Before dehorning, calves approached 73% of ambiguous screens, but only 66% after. Likewise, before separation, calves approached 72% of ambiguous screens, but only 62% after.
The researchers saw this as a negative response bias – scientific talk for what we might call a bad mood – or negative emotional state. The UBC researchers say this is the first evidence of a cognitive response to separation from a mother in any species. Previous works showed only behavior changes and physiological changes like vocalization and activity.
Source: PLOS ONE