Pessimistic calves at disadvantage

Researchers have discovered that some calves are more fearful than others, which can have implications for future health

Some cattle are more fearful than others. It’s a universal truth confirmed by anyone who has handled cattle herds.

But fearfulness is connected to pessimism, says University of British Columbia PhD student Benjamin Lecorps. His research on 22 Holstein dairy calves has shown that some animals are inherently more pessimistic than others, and that trait tends to persist over time. The finding could have implications for the animals’ future health and productivity.

“We know that pessimistic people tend to be more vulnerable to stress, to react more intensely and to cope very bad with it, so we wondered if that was true for optimism and pessimism in calves,” Lecorps said.

He said optimism and pessimism have been studied in other animal species, as well as in people. The terms suit the situation and are not an example of anthropomorphism, the practice of attributing human characteristics to people.

“It is often tricky to find a good label. I guess in the case of optimism, it’s quite safe.”

His research first involved training the calves to understand choices that would lead to a reward. The method was described in a UBC news release.

An infrared camera was used to measure the calves’ eye temperature after being transported. A higher temperature, indicated in the lighter colours, is associated with higher stress. | UBC photo

“In the training, each calf entered a small pen and found a wall with five holes arranged in a horizontal line, two-and-a-half feet apart. The hole at one end contained milk from a bottle, while the hole at the opposite end contained only an empty bottle and delivered a puff of air in calves’ faces. The calves learned quickly which side of the pen held the milk reward.

“Once calves were trained, researchers presented bottles in one of the three intermediate holes, so that calves couldn’t be sure if they would be rewarded with milk.”

Upon observation, researchers found that some calves were more reluctant than others to investigate the nipples and seek a reward.

Tests several weeks apart showed the same calves reacted in the same ways.

“Our results indicate that calves differ in their base line levels of pessimism and optimism, and do so in a consistent way over a period of three weeks,” Lecorps and colleagues wrote in a paper published in Scientific Reports.

“To our knowledge, this is the first time that consistency in judgment bias over time has been demonstrated in farm animals.

“These findings have implications for animal welfare, as more pessimistic animals may fail to seize opportunities that are commonly assumed to provide good welfare (e.g. environmental enrichment).”

Four months later, Lecorps and his research colleagues tested the calves again, this time by transporting them in a trailer for two 10-minute trips.

They measured the number of moos emitted by the calves and also measured their eye temperature with higher temperatures being an indication of stress.

They found that the calves already determined to be more pessimistic also showed higher stress levels in transport.

“Improving our understanding of how individuals differ will probably improve the way that we manage calves and cows,” said Lecorps.

Though people tend to manage cattle using methods that are good for the average, “that doesn’t mean that every individual is coping well with the situations we are using in management.”

Though it hasn’t yet been shown in research, Lecorps speculated that the pessimistic animals would be more vulnerable to stress and thus more susceptible to illness.

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