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Clintonville — Most dairy farms use some form of dry-cow therapy, noted Dr. Pam Ruegg, DVM, as she began her presentation during the opening session of the annual Cow College at the Fox Valley Technical College Regional Center.

The session was the first in the 2017 series presented by the University of Wisconsin Extension agricultural agents in Outagamie, Shawano and Waupaca counties designed to connect dairy farmers and industry representatives from Northeast and East Central Wisconsin with resources from the UW system sharing the latest research and information affecting the dairy industry today.

Ruegg, Extension Udder Health & Milk Quality specialist at UW-Madison, says the use of antibiotic dry-cow therapy at the end of lactation is a standard part of mastitis control programs, and in the United States it is highly adopted.

“USDA National Animal Health Monitoring Survey data show more than 80 percent of US dairy herds treat 100 percent of the quarters of their cows at the end of dry off, and almost all herds treat a majority of all quarters,” she commented

“However, today we are undergoing a reexamination of the use of antibiotics on dairy farms with the goal of using antibiotics more responsibility and for only animals that will benefit.” Ruegg stressed.

“When we talk about reducing antibiotic use, the only way we can do that is by changing the way we treat and prevent mastitis because 65-85 percent of antibiotics are used to treat mastitis and 30 percent of antibiotic usage is in dry-cow therapy. “On average, five doses of antibiotics are used per year to treat a cow over a three-to-five-day period, so there isn’t much room to reduce antibiotic use,” she pointed out.

Ruegg noted that dry-cow therapy (DCT) was originally developed primarily to reduce the prevalence of Staph aureus and Strep agalactiae bacteria that cause long-term subclinical infections.

“We’ve done a great job of controlling these, but today environmental pathogens tend to cause most cases of clinical mastitis rather than long-term chronic infections, and we have lots more healthy cows at the end of lactation,” she observed.

Because of improved herd health and lower somatic cell counts (SCC), Ruegg says many producers are wondering whether it is still relevant and profitable to invest in dry-cow therapy for every quarter of every cow at the end of lactation.

“The dry period itself has enormous risks for the development of bacterial infection in the udder,” she emphasized. “During the early and later parts of the dry period, cows have an udder full of milk, and milk is a fantastic growth media for bacteria; we also stop cleaning the teats at this time.”

Leaking milk is one of the largest risk factors for the development of mastitis, and increases the risk seven times over a cow that’s not leaking milk. according to Ruegg.

She says there are two primary ways to reduce the risk of mastitis in the next lactation. “One is to treat the cows with antibiotics that have developed long-term subclinical infections; the other purpose is to prevent the development of infection during the high-risk period.”

Treating the infected cow at dry-off increases efficiency, reduces risk of drug residue and is more economical because no milk has to be discarded. A Keratin plug is an effective way to prevent mastitis causing bacteria from entering the teats.

Effectiveness of DCT

Ruegg reported that dry-cow therapy has been shown to cure 70 percent of intra mammary infections (IMIs) that are susceptible to the drugs used, and reduces new IMIs by 50-75 percent.

She says cows that remain infected across the dry period pay a high price in lost milk production, risk of infecting other animals and an increased risk of clinical mastitis. “Studies have shown cows with an SCC of 150,000 have twice the risk of a clinical case, and that early lactation mastitis decreases first-service conception rates,” she related

Many producers are now employing selective DCT. “Its purpose is to administer antibiotics to only cows that show evidence of an intra-mammary infection at dry-off, and prevent new infections using teat sealant,” said Ruegg.

She noted that identifying cows with active infections is done by reviewing the cow’s history of clinical mastitis, reviewing monthly SCC history and performing tests on individual quarters.

“Research on dairy herds in Ohio, the Netherlands and Canada indicate that selective DCT, when applied randomly, decreases antibiotic use but can increase mastitis, while DCT, when carefully applied, can decrease antibiotic use without increasing mastitis or antimicrobial resistance,” Ruegg related.

“Selective dry-cow therapy may be appropriate for your herd if you are able to adequately monitor the monthly SCC values of individual cows, perform fore stripping to identify clinical mastitis and review mastitis records,” she said.

Cost of DCT

Cows that should be considered for selective dry-cow therapy are those with a SCC of 150,00 at their last monthly test, and those with a history of clinical mastitis within 90 days of dry off.”They should receive antibiotic treatment in every quarter,” Ruegg said. “Those with no recent history of clinical mastitis are eligible for teat sealant only,”

Breaking down the per-cow cost of dry-cow therapy, Ruegg reported the price for a single dose of Orbeseal is $10.50, and Spectramast DC is $19.50. “If you use Tomorrow instead of Spectramast, the cost would be less,” she said. “Dry-cow treatment with antibiotics and sealant would range from $20-$30 per cow.”

Ruegg emphasized that even during periods of low milk prices dry-cow therapy makes economic sense for producers because it’s relatively inexpensive compared to the cost of mastitis.

“It does require any investment to control udder health, which also includes the cost of teat dip, sand bedding and vaccinations.” she remarked. “in a 200-cow dairy, it costs about $2,300 a month.”

Every year mastitis is costing similar sized dairies about $82,000, which includes $32,000 in prevention. “So, 36 percent of our total cost is prevention. Our biggest single loss is in milk production due to sub-clinical mastitis and culling costs,” she stressed.

“You need to be careful in making the decision to use a selective dry-cow program,” Ruegg advised. “Dry-cow therapy can be effective in some herds, but risks versus gains need to be carefully assessed. Selection of cows that need to receive therapy is not a perfect science, and herds using selective therapy should have good post-calving surveillance programs.”

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