Cows licking each other around the head and neck is the sign of a healthy herd, according to new research writes Tom Campbell.

Cattle social grooming behaviour - known as allogrooming - helps cows forge strong friendships and keeps harmony in the herd, say scientists.

Dairy farmers regularly shuffle cows into different groups, forcing the animals to re-establish their social network, which has a negative effect on the animals' behaviour, health and productivity, according to previous research.

Lead author Dr Gustavo Monti, of the Austral University of Chile, said: "Our aim was to understand how social networks are formed by cows after they are reunited at the beginning of the milking period, and what factors may influence these changes.

"This is important because cattle form strong bonds, which offer them social support and help them cope with the stressors that occur regularly in dairy cows' lives."

The team observed a small herd of dairy cows, which had recently given birth at a pasture-based dairy farm in the city of Valdivia, South-Central Chile.

More than 1,300 "allogrooming events" were recorded between almost 40 cows during the month-long experiment.

A statistical modelling technique, which had never been used on animals before, known as stochastic actor-oriented modelling (SAOM), was used to map the cattle's social behaviour.

Cows tended to groom other members of the herd if they had returned the favour in the past or if they were around the same age, the researchers found.

South West Farmer:

Picture: Gustavo E. Monti / SWNS

Older cows were generally more likely to groom others than younger ones, while the most "active groomers", who did not have a preferred grooming partner, received less attention as time passed.

Dr Monti said: "Our results indicate that licking behaviour is important to make friends and to maintain harmony in the herd.

That older cows groom more individuals suggests that they take the role of "peacemakers" in the herd."

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Preferring a grooming partner of the same age could also be because the animals grew up together.

Dairy farmers repeatedly separate cows depending on factors such as, the milk they produce - or lactation stage, their dietary requirements and breed.

Dr Monti said: "It is important for farmers to be mindful of the relevance of the social aspects of the lives of cows, animals that form complex emotional relationships within their group.

"Farmers should be aware that cows frequently grooming each other is a positive sign that means that those cows get along."

Chopping and changing the herd breaks the animals' social network and can have negative effects on their health and productivity.

Dr Monti added: "On the contrary, if social grooming declines, it may be a sign of impaired welfare.

"This new knowledge should be translated into innovative practical strategies that will result in the continued integration of cattle emotional and social needs into management systems."

There are nearly two million dairy cows in the UK, spread across over 14,000 farms.

To produce milk, the cows must give birth to a calve, meaning around two million dairy calves are born in the UK every year.

The findings were published in the journal Frontiers in Veterinary Science.