Moo swings? Cows go through disruptive puberty too – study

Ian Sample
Photograph: Alamy

Humans are not alone in enduring the rollercoaster ride of puberty as powerful hormones flood the body and cause mood swings from one day to the next. Scientists have found that dairy cows pass through a similar phase of emotional confusion that disturbs their otherwise rather stable personalities.

The findings emerged from extensive observations of Holstein dairy cattle as they matured from calves to adulthood. “Our study identified a period of inconsistency in personality traits over puberty,” said Nina Von Keyserlingk, a professor of animal welfare at the University of British Columbia in Canada.

Some animals became more shy during puberty and others became more bold. Some became less interested in nosing up to new people or objects while others became more so.

The work sheds light on an under-studied realm of bovine life. Previous attempts to ascertain cattle personalities at different ages have found that they are reasonably stable in youth and in adulthood. Puberty, however, was something of a mystery.

Von Keyserlingk and her former student Heather Neave assessed the cows for two personality traits by placing them in a test arena and watching how they behaved alone and around unfamiliar objects or strangers. The scientists ranked the animals first for boldness and second for how eager they were to explore. The tests were performed on calves at the ages of one and three months, one year and two and a half years.

The findings, reported in Royal Society Open Science, suggest that while cows have stable personalities as calves and adults, in between those ages when puberty hits their behaviour becomes less predictable.

Scientists hope that understanding cattle personalities and how they might vary with age will help improve animal health and farming practices. Previous studies have found that cows that become more stressed tend to eat less, grow slower, have weaker immune systems and produce less milk.

“Our overall goal is to improve the lives of animals on farms,” said Neave. “Ideally, in the future, management practices would be tailored to the individual rather than the herd, so that all calves and cows have an opportunity to thrive on the farm and reach their full productive potential.”

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Lori Marino, a neuroscientist and executive director of the Utah-based Kimmela Center for Animal Advocacy, said she was not surprised by the findings, as puberty was “a time of tremendous change both physically and emotionally”.

Marino, who co-authored a recent study, The Psychology of Cows, added: “It is a time when humans, too, are quite volatile in their moods and personality traits. This finding again demonstrates how similar we all are, whether we are cows or primates.

“Of course, it makes pubescents less predictable and that can translate into how we interact with them. But in the end it tells us that if cows and humans share so much of their psychology with each other, we need to look at cows as beings who also have feelings about being farmed and having their children taken away from them in the dairy industry.”