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Dairy cow grooming behavior reveals complex social networks

August 4, 2020

Like people, cattle are social creatures with complex relationships that change as group dynamics evolve, and a study published in Frontiers in Veterinary Science is offering new insights into the social networking behavior of dairy cows, building on a body of research that could someday help reshape farm management practices to create healthier living environments for the animals.

A team of researchers in Chile and the U.S. spent 30 days observing a small herd of dairy cows that had recently given birth to understand the web of bovine interactions based on social grooming behavior, also known as allogrooming, an announcement from the journal publisher said.

In modern dairy production systems, cows are frequently shuffled into different groups depending on factors such as lactation stage, nutrition requirements and breeding, the announcement said. The animals must re-establish their social structure during each regrouping, which previous research has shown causes negative effects on behavior, health and productivity.

Allogrooming, which generally involves one cow licking another around the head and neck, is believed to serve a number of social purposes, the researchers said. For instance, social grooming is a way to establish individual bonds between members of a group and also enhances the herd's overall social cohesion.

"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," said lead author Dr. Gustavo E. Monti from the Institute of Veterinary Preventive Medicine at the Austral University of Chile.

The study took place at a pasture-based dairy farm at an agricultural research station in the south-central city of Valdivia, Chile. Researchers recorded a total of 1,329 allogrooming events from 38 cows during the month-long experiment.

Their observations uncovered a variety of patterns based on different attributes, such as each animal's age and social rank. For example, cows tended to groom individuals that had previously groomed them, implying mutual cooperation, the researchers said. They also tended to prefer individuals of similar age, suggesting a certain familiarity because they grew up together.

Meanwhile, the most active groomers that did not seem to prefer specific individuals actually received less attention from other group members over time. Older individuals groomed more cows than younger ones, suggesting that allogrooming could be related to seniority, the researchers suggested.

"Our results indicate that licking behavior 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," Monti said.

The observational study used a modern sociological research method called social network analysis, which reconstructs social interactions graphically using nodes that represent individuals and links that refer to relationships that connect them, the announcement explained.

While such analyses have been used to understand animals' social networks, this research is one of the first to employ a statistical modeling method known as stochastic actor-oriented modeling (SAOM) to mammals other than humans. The SAOM framework crunches data on individual attributes and group dynamics to understand how group members change their relationships over time.

"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. 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," Monti said.

Other researchers involved in the study include Inés de Freslon and Ana C. Strappini with Universidad Austral de Chile and J.M. Peralta with the Western University of Health Sciences' College of Veterinary Medicine in Pomona, Cal.

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