“Mastitis is still the No. 1 reason we use antibiotics in adult dairy cows,” says Ron Erskine, Michigan State University veterinarian.
Used effectively, they can/will reduce mastitis
Editor’s note: This is the first of a series of articles on mastitis, treatment protocols and new research.
The Food and Drug Administration requires all farms that use prescription antibiotics to have a valid veterinarian/client/patient relationship and written treatment protocols.
Simply meeting that legal requirement is just the first step in proper antibiotic use. More importantly, the protocols are a critical tool in mastitis monitoring and control, reducing residue risks and ultimately, cow and herd health, says Ron Erskine, a veterinarian and milk-quality specialist at Michigan State University.
"You really need a comprehensive plan. Mastitis is still the No. 1 reason we use antibiotics in adult dairy cows," he says. "Plus, there are a lot of costs to mastitis—milk losses, drugs, labor, relapses—even embryo losses and reproductive issues.
"First and foremost, treatment protocols must be set up with your veterinarian," Erskine says. The protocols should include all the little things, such as cow identification, what defines a clinical case of mastitis that requires treatment, cleaning of the teat prior to infusion, what to do if the case is a relapse of a prior infection, the recording of the treatment and milk withhold time.
"Treatment protocols are lot more than what drug to use, how often it is used and at what volume," he says.
Culturing is an important tool in developing your protocol. You should first determine which microorganisms are the main causes of mastitis on your farm. Gram-positive bacteria, such as Streptococcus species, staphylococci or new (not chronic) cases of Staph. aureus, tend to respond to antibiotics better than other pathogens.
"There are two major reasons we get treatment failure," Erskine says.
The first is repeat chronic infections. This is not so much about resistance to the drug being used as changes in the infected quarter that no longer allows the drug to reach the bug, he says.
The second reason for failure is that some pathogens, such Prototheca, Pseudomonas and fungal infections have very little chance of treatment success. Other pathogens, such as E. coli, might have already resolved themselves and be on the way to self cure.
Culturing isn’t fool-proof. Some 30% of cultures won’t isolate any organism. And contaminated samples will only confuse the issue. "But culturing can help identify which cows to treat and which are not likely to respond to antibiotics," Erskine says.
Protocols should also identify who in the parlor makes the treatment decision and who actually treats the cows. Key to all of this is worker training—and retraining. "Protocol drift is a real problem, and retraining at least a couple of times each year is important," Erskine says.
"And that assumes there is no turnover," he says. Some dairies have 20% to 30% annual turnover, so protocols are worthless if new employees aren’t trained in their use.
Once protocols are established, monitoring results is the only way to know if protocols are being followed. There are several ways to validate protocols.
The first might simply be a monthly inventory check on the number of mastitis tubes used each month. By checking treatment records, you should know how many cows were treated and how many antibiotic tubes should have been used.
That still won’t tell you if the protocols are actually getting clinical cures. For that, you need to check relapse rates periodically.
"Relapses are perhaps the simplest measure of treatment success," Erskine says. "Unfortunately, many farms don’t have a good handle on what their relapse rates are."
You also need to take a long-term look at relapse rates. Fourteen to 21 days is too short, he says, because the mastitis can revert to subclinical and not be truly cured. Then, a month or two later, it again flares into a clinical case.
Erskine recommends placing a band on the cow’s leg the first time she is treated. This band should be a different color than a band used to indicate that her milk should be withheld. The treatment band should remain on the cow once she returns to the milking string. Then, if she has mastitis again, employees will automatically know that she has been treated for mastitis before.
A decision can then be made on how or whether she should be retreated. "Many times, workers are doing their job treating cows. But dairy managers aren’t doing theirs—monitoring relapses or checking records," he says.
Individual cow somatic cell counts (SCCs) or in-line conductivity can also be used to monitor cure rates. "If treated cows have a linear score of 3 or less or an SCC of 100,000 or less, the probability of an infection is pretty low," Erskine says. "But it does take a couple of weeks for SCC to ramp down. After three or four weeks, SCCs should be down."
Survey Results Mixed
A survey of more than 600 dairy farmers in Florida, Michigan and Pennsylvania shows good adoption rates of recommended mastitis control practices such as teat dipping, use of individual towels and dry cow therapy.
But the results also suggest that mastitis educators have a ways to go. "Critical behaviors that are believed to reduce the use of unproductive antibiotic therapy for mastitis, such as recording all treatments (47%), review of treatment records to identify previous treatments (42%) and bacterial culture of milk from clinical mastitis cases (15%) were reported as ‘always or frequently’ done," says Ron Erskine, veterinarian at Michigan State University.
"Although 73% of herds ‘always or frequently’ assured strict compliance of milking protocols, only 63% reported that they trained employees," he adds.
It’s clear more education is needed, since 38% of respondents said natural therapies were among their top three choices to reduce antibiotic use. Treating cows for the full regimen of prescribed doses was listed by only 35% of respondents.
The survey was done by the Quality Milk Alliance and funded by a USDA National Institute of Food and Agriculture grant. The goal of the Alliance is to reduce mastitis by one-third and antibiotic use by half in the next five years. Michigan State University, Florida A & M University, Penn State University and Mississippi State University are participating in the effort.
- March 2014