April 10, 2023 at 3:09 p.m.
Benefits of selective dry cow therapy
Dr. Daryl Nydam, of Cornell University, was at the Professional Dairy Producers annual business conference March 15 to discuss the pros and cons of selective dry cow therapy in his presentation, “Dollars and Sense in Udder Health.”
“Sixty percent of antimicrobial usage in the dairy industry is aimed at control or treatment of mastitis, and two-thirds of that is dry cow therapy,” Nydam said. “Dry cow therapy is the only place in the dairy industry where we kind of routinely use antibiotics.”
Nydam said the thought process of blanket dry cow therapy dates back to the early 1960s.
“My father was a veterinarian, and he was at the forefront of, ‘Treat every quarter, every cow with a tube,’” Nydam said. “That made it into the National Mastitis Council’s five-point plan, and when they made it a 10-point plan, it stayed in there. I think nothing has been more adopted than dry cow therapy.”
Nydam said a recent U.S. Department of Agriculture survey found that 93% of cows in the U.S. are treated with intramammary antimicrobials at dry-off.
“I think that is more cows than are fed with a (total mixed ration) and more than are bred with AI right now,” Nydam said. “We have adopted this wholeheartedly. So, why am I here to tell about selective therapy? It was an awesome thing when the average dry cow either had or was likely to acquire a new infection. When blanket therapy started, most of the quarters had a sub-clinical infection.”
Research conducted in 1985 found that 45% were cultured negative, Nydam said, meaning that more than half of quarters were cultured positive. Nydam’s current research has found that between 75%-90% of quarters are cultured negative.
“Udder health has dramatically improved in the United States,” he said. “Back then, it didn’t pay to try and sort out which cows to treat and not to treat. It was more economical and probably a good use of antibiotics overall.”
Nydam said the pathology of the infections has changed over the last quarter century.
“Back in the day, Strep ag was a huge problem, and fortunately, Strep ag dies with any of the six brands of dry cow tubes,” Nydam said. “It’s a great way to clean it up in a herd. Staph aureus used to be a big problem in herds, and now, it is typically a very small problem. But those contagious pathogens were highly prevalent. Now, we see mostly E. coli, Klebsiella, Strep non-ag and Staph non-aureus. They are more sporadic, and only 10% of the quarters are infected at dry-off.”
New protocols for udder health at dry-off have also helped.
“We have a bunch of teat sealants, and they work pretty darn well at preventing new intramammary infections during the dry period,” Nydam said.
When it comes to selecting dry cow treatments and teat sealants, Nydam said research has shown there is little difference among any of the available products, which he said allows producers to feel comfortable using the one that is most cost-effective for them.
“We’re in the dairy business, and our first order of business is to make money,” Nydam said. “We have to do this without compromising animal health because we care for these critters, and it turns out, good health and productivity usually go hand in hand. We can save money on tubes, and perhaps labor, if we selectively treat cows.”
Nydam said selective dry cow therapy might also decrease the risk of residues in early lactation.
“There is a track record of safety in our industry like none other,” he said. “I’m proud to say 0.018% of tankers in the country leaving the farm last year had a residue, but we can always do better.”
Nydam said selective dry cow therapy might, at some point in time, play into what he calls our social license to sell milk.
Each year, Nydam said he sends a letter on behalf of Cornell University to the New York state government, explaining why he thinks banning blanket dry cow therapy is a bad idea. He said legislation like this has passed in some states and keeps coming up in others, and blanket therapies may be outlawed as they are in much of the European Union.
“I want us to be ahead of that game, so we can say that we as an industry are policing this ourselves,” he said. “I don’t want someone in a state capital telling us how to best run our farms.”
To implement selective dry cow therapy, Nydam said the first step is determining which cows and quarters require treatment.
“To do this, we need something that is pretty accurate, pretty rapid and inexpensive,” Nydam said. “I would say it’s going to have to be less than $10 to $12, because that would be a savings on tubes. If it is more than that, no one will buy it.”
Nydam said culturing is probably the most accurate way to detect an issue and can be done at the quarter-level. The downside of culturing is the expense and time needed to complete the culture. On-farm data can also come into play, such as from testing programs, which can provide individual cow somatic cell count data and records of mastitis events.
Nydam has worked on several studies that have shown no discernible differences between cows that are blanket-treated and cows that are selectively treated at dry-off.
“Even if we see a slight decrease in udder health overall, we are still coming out ahead using selective dry cow therapy,” he said. “Selective dry cow therapy can help decrease our overall on-farm antibiotic usage.”
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