DULUTH, Ga. (December 8, 2022) — “We’ve come a long way in the past 50 years,” said Linda Tikofsky, DVM, Boehringer Ingelheim. “The dairy industry has made significant improvements to cow comfort and nutrition, as well as mastitis treatment and detection.”
As the industry continues to advance, it may not make sense for all producers to continue using blanket dry cow therapy. Selective dry cow therapy (SDCT) — in which antibiotics are only used to treat cows with likely intramammary infections at dry-off — is an opportunity for producers to cut down on antibiotic use by as much as two-thirds.1
There are two schools of thought on how to implement SDCT:
- Culture-based SDCT collects and cultures milk samples two days before dry-off. Cows that have one or more quarters test positive for mastitis are given antibiotics.
- Algorithm-based SDCT uses records from farm management software. Cows that meet any of the following criteria are treated:
- Somatic cell count (SCC) averaging 200,000 or greater on the last three tests and the last test before dry-off
- Any clinical mastitis cases in the last 14 days before dry-off
- Two or more clinical mastitis cases during the current lactation
A study compared culture-based versus algorithm-based SDCT and found no difference in efficacy. All of the study herds were able to reduce antibiotic use by about 60% without negatively affecting cow health or milk production.2,3
“SDCT can offer many benefits, but it’s not right for every herd,” emphasized Dr. Tikofsky. Before you start a program, make sure you’re fulfilling the following checklist:
- Your herd SCC is consistently less than 200,000. If your dairy frequently bumps up over 200,000, or even 150,000, then SDCT isn’t the right fit.
- Your herd is free of contagious mastitis. For herds that struggle with contagious mastitis, most commonly caused by Staphylococcus aureus, SDCT is not a viable option. Dry cow therapy is one of the most effective tools against contagious mastitis because it will tackle subclinical infections at dry-off.
- You participate in a milk testing program. Collecting milk through the National Dairy Herd Improvement Association on a monthly basis is an excellent way to track the proportion of cows that struggle with mastitis or have a consistently high SCC. The data can help producers choose the cows that need treatment at dry-off versus the ones that don’t.
- You keep thorough records. SDCT requires outstanding data analysis and record keeping. Dairy employees should be meticulous when collecting, organizing and handling data, so the right cows are treated at dry-off.
- You use a teat sealant. “We’ve learned that more than 25% of cows don’t form a keratin plug at dry-off,” said Dr. Tikofsky.4 “So, if we’re not using an antibiotic in those quarters, we need to make sure we’re giving cows physical protection with an internal teat sealant.”
- Your staff is well-trained. An SDCT program is most successful when staff are well trained and have a comprehensive understanding of dry cow procedures.
- You use a coliform mastitis vaccine. Coliform mastitis is the source of 50% of mastitis infections in U.S. dairy herds.5 “We want to make sure we’re protecting cows with vaccination,” advised Dr. Tikofsky. “An effective mastitis vaccine should have a short meat withdrawal and provide coverage against Escherichia coli and endotoxemia caused by E. coli and Salmonella Typh
imurium.” - You ensure high-producing cows are ready to be dried off. Cows that are dried off giving large amounts of milk can experience serious udder engorgement, and they are also more likely to leak milk and become infected. Utilize a supplement at or 8-12 hours before dry-off to reduce udder engorgement and help cows transition more comfortably into the dry period.
“If you feel confident in your mastitis management practices, it’s time to bring your veterinarian and employees together to discuss SDCT implementation options,” noted Dr. Tikofsky. “There’s less forgiveness in SDCT, and it requires a team approach.”
Once SDCT is implemented, it is crucial to monitor and evaluate the program. An ideal monitoring program includes:
- Regular bulk tank cultures to test for contagious mastitis pathogens
- Routine SCC testing
- Culturing clinical and chronic mastitis cases
- Monitoring cows for mastitis during the dry period
- Monitoring clinical mastitis rates and SCC in early lactation
- Veterinary involvement and evaluation of records
“A lot has changed in the last 50 years, but producers have remained committed to animal stewardship,” concluded Dr. Tikofsky. “Moving forward, I think we’ll see more of a switch to selective therapy. It’s a way to be extraordinarily proactive, and can have a lasting impact on animal health, food safety and consumer confidence in dairy products.”
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