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Serving: MN

New University of Minnesota dry cow program reduces antibiotic use

Martin Moen, U-MN cow receiving dry-cow mastitis treatment
ONLY INFECTED COWS: The practice of treating all lactating dairy cows with a dry-cow mastitis treatment at dry-off has the potential to fall to the wayside with a new selective dry cow therapy program developed by the University of Minnesota.
The selective therapy program proves that routine dry cow antibiotic use can be cut in half.

A University of Minnesota College of Veterinary Medicine team has developed a new dry cow treatment program that could help dairy farmers reduce antibiotic use in their dry cows by up to 55%.

The new selective dry cow therapy program relies on rapid pathogen testing that identifies quarters infected with mastitis for treatment. Teat sealants are then used on all four quarters, treated and untreated.

Sandra Godden, U-MN CVM professor, led the multi-state research team in validating two different approaches to selective dry cow therapy.

As background, she explains how somatic cell counts in milk, an indication of udder health, have tremendously decreased over the last 10 to 15 years as farmers have improved cow care and helped eradicate strep ag and minimize staph aureus udder infections.

“At dry off, we’re seeing a lower prevalence of mastitis infection with about 15% to 20% of quarters infected in well-managed herds,” Godden says. “It only makes sense to only treat those quarters on those cows that are infected, rather than dry treat all quarters on all cows.”

Veterinarian Sandra GoddenTEAM APPORACH: Veterinarian Sandra Godden, University of Minnesota, led a multi-state researcher team that evaluated programs to reduce antibiotic use in dry cows.

Low mastitis prevalence, coupled individual quarter testing and teat sealants, are important components to a successful dry cow therapy program, she says.

To prove that a selective program would work, Godden and her team collaborated with researchers in New York, Iowa and California to evaluate two ways of reducing dry cow antibiotic use—by relying on a cow’s records showing her past mastitis history in that lactation and by confirming infection with culturing each quarter prior to dry-off.

The algorithm-guided selective treatment program called for cows to receive dry cow antibiotic in all quarters if they had clinical mastitis at least twice that lactation or if they had one or more DHIA SCC tests higher than 200,000 cells per milliliter.

The culture-based program required collection of quarter milk samples two days before dry-off. Samples were plated and incubated for 36 hours using a rapid culture system developed at the University of Minnesota — the Minnesota Easy 4Cast plate. Only individual quarters culturing positive for bacterial growth were treated with antibiotic at dry-off. All quarters of all cows were treated with an internal teat sealant.

Both programs were compared with a blanket antibiotic treatment protocol. The trial involved seven dairy herds and more than 1,200 cows. All cows were followed to 120 days in milk to evaluate the impact of the dry-off programs on future lactation health and performance.

At the conclusion of the trial, both the algorithm- and culture-guided programs reduced antibiotic use on average by 55%, compared to the blanket dry cow treatment, without any negative effects on the next lactation or performance, Godden says.

A second research project looked at the economics of the two selective therapy programs and compared them to blanket dry cow therapy. On average, the algorithm-guided selective treatment program had a $7.85 per cow savings at dry-off and the culture-guided, $2.14 per cow savings. The difference in savings between the two is because the algorithm data was free to use while it cost approximately $4 per cow in labor and supplies to culture a cow, Godden adds.

Set up for success

Selective dry cow therapy is not for every herd, Godden says.

Having a successful program will depend on farm management, current SCC levels and the farm’s ability to monitor. Ideally, a dairy herd would have an annual bulk tank SCC average less than 250,000 cells per milliliter, no strep ag infections, correct hygienic technique at dry-off, teat sealant applied to every cow at dry-off and a monitoring program to track results.

And with the culture-guided program, the farm either needs its own rapid culture equipment or to work with the farm’s veterinary clinic to perform the culture work.

Godden encourages farmers to work closely with their herd veterinarian to decide if they are good candidates to adopt the selective dry cow therapy program and then to develop, implement and monitor it.

University of Minnesotatest petri dish

CULTURE TO BE SURE: A key element to the University of Minnesota’s new selective dry cow therapy program is rapid test results to check for mastitis in milk. University researchers developed the Minnesota Easy 4Cast plate a few years ago to aid in collecting milk samples from a cow’s four quarters.

In Minnesota, more than half the DHIA herds already fit the criteria, Godden says. When the researchers presented their findings last spring, Minnesota DHIA determined that in April and May 2020 alone, 59% of the herds were eligible and of that number, 79% of the cows — 10,043 cows — would not need dry cow antibiotic treatment.

“That’s a huge potential reduction in antibiotic use and associated costs savings for producers,” Godden says.

Beginning in November, Minnesota DHIA will list upcoming dry cows as high or low mastitis risk on its SCC 370 Flex Report.

“Farmers using this report would still need to check a cow’s clinical mastitis history,” she adds.

Interested in comparing costs of the blanket, algorithm- and culture-based dry cow therapy programs on your farm? Check out U-MN’s online cost calculator

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