By following new recommendations from Cornell for smarter, more targeted antibiotic use, New York dairy farmers can save money and have healthy cows while slowing the rise of antibiotic-resistant bacteria. But not all farmers are following the new guidelines.

To find out why, an interdisciplinary team of researchers from Cornell and the University of Wageningen in the Netherlands used a social psychology approach to understand how dairy farmers’ views impact how and when they use antibiotics to treat their cows.

In a new paper in PLOS One, they report that farmers make these changes when they are confident they won’t disrupt their operations. Also, hearing success stories from others in the dairy industry may be the best way to empower farmers to adopt the new strategies.

“We wanted to understand better what drives farmers’ perceptions of how they are stewards of antimicrobial use,” said Daryl Nydam, professor at the College of Veterinary Medicine and faculty director of the Cornell Atkinson Center for Sustainability.

Nydam and Lorin Warnick, the Austin O. Hooey Dean of Veterinary Medicine, assembled an interdisciplinary team that included veterinarians, epidemiologists, a behavioral economist and an expert in agricultural economics. They received a grant from the Atkinson Center.

Working with the New York State Department of Agriculture and Markets, the team sent anonymous and confidential surveys to all of the state’s nearly 4,000 dairy farms, and received more than 400 responses. The survey included questions about current antibiotic use and farmers’ attitudes toward “prudent use of antibiotics” – only using the drugs when diagnostic tests or cattle records indicate treatment is necessary. The researchers also asked about social norms surrounding prudent use and perceived barriers to implementing the strategies.

For many reasons, dairy farmers want to keep antibiotic use to a minimum. The drugs are costly, and milk with antibiotic residues can’t be sold. However, treatment is sometimes necessary to treat mastitis, a common udder infection, or to control an infection after “dry-off,” when a cow stops being milked toward the end of pregnancy.

“Currently, many dairies are blanket-treating cows with antibiotics, which means that if a cow comes in with mastitis, it receives an antibiotic,” said co-author and former postdoctoral researcher Amy Vasquez, who recently accepted a job with a dairy technology company in Sweden. Many farmers also blanket-treat cows at dry-off.

Previous studies by Nydam, Vasquez and colleagues have shown that about two-thirds of non-severe cases of mastitis will clear up on their own, and that bacterial testing can identify the infections that require treatment. They also developed an algorithm farmers can use to identify cows that need preventive treatment at dry-off. When tested on farms, both strategies reduced antibiotic use associated with udder health by around 50% to 60% without negatively affecting cow health or milk production.

“We’re finding that the management practices on these dairies are so good – they are so clean and disease-free – that maybe we don’t need to be treating cows prophylactically,” Vasquez said.

When the researchers analyzed the survey responses, they saw that confidence was the most important factor driving farmers to select prudent use strategies. “The more that farmers are given tools to understand the decision they are making, the better,” Nydam said. These farmers believed that selective treatment would increase profitability and that the new testing protocols could fit into their daily routine.

The survey also showed that farmers are most receptive to the opinions of fellow farmers, veterinarians and milk processing plants regarding antibiotic use. As a result, success stories from farms that have become more profitable through reduced antibiotic usage – especially when told by trusted members of the dairy industry – may be the most effective way to give farmers the confidence boost needed to adopt these changes.

“If we can spread those strategies through trade shows, producer meetings and veterinary conferences, then I think that’s the way to go,” said Vasquez.

Co-authors include postdoctoral researcher Carla Foditsch, student researcher Stéphie-Anne Dulièpre and research technician Julie Siler of the College of Veterinary Medicine; David Just, professor at the Dyson School of Applied Economics and Management; and Jaap Sok, professor at Wageningen University.

Patricia Waldron is a freelance writer for the College of Veterinary Medicine.