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Ruegg: Mastitis bacteria changing? Yes. Increasing resistance? Not so much – Audio

[audio:|titles=Pam Ruegg on new mastitis discoveries]
Pamela Ruegg, Professor, Extension Milk Quality Specialist
Department of Dairy Science
UW-Madison College of Agricultural and Life Sciences
(608) 263-3495

Evolution of costly dairy cow disease

3:04 – Total Time
0:16 – What mastitis is
0:30 – New discoveries
0:56 – Surprises in the research
1:22 – Reason for the surprise
1:45 – Implications for dairy business
2:18 – Antibiotic resistance not increasing
2:54 – Lead out


On the trail of a costly dairy cattle disease. We’re visiting today with Pamela Ruegg, Department of Dairy Science, University of Wisconsin Extension in the College of Agricultural and Life Sciences, Madison, WI and I’m Sevie Kenyon.

Sevie Kenyon: Pam, tell us what this disease is?

Pam Ruegg: So, mastitis is a bacterial infection of the udder. The interesting thing about this disease is virtually every farm experiences it. They experience it typically in a fairly large percentage of cows.

Sevie Kenyon: What new things are you discovering?

Pam Ruegg: In 2010, we visited 52 dairy farms here in Wisconsin. We were targeting farms that had more than 200 cows. We did that because the management of these farms has been changing dramatically yet they were still experiencing a lot of clinical symptoms of mastitis on their dairy farms and we wanted to look at some of the pathogens that were causing that, the bacteria, and also some of the management strategies relative to controlling it.

Sevie Kenyon: Where there some surprises in your findings?

Pam Ruegg: There were! When we took the milk samples from those cases, our most common finding on what was causing the mastitis is we had a milk sample where no bacteria could be recovered. Yeah. So, we have a cow, she’s got abnormal milk, the farmer recognizes that she has mastitis, we take a milk sample, we take it to the laboratory, and when we look at that “plate” that we put in the incubator the next day there’s no bacteria.

Sevie Kenyon: So what’s happening to it? Where is it?

Pam Ruegg: What we’re dealing with are what we call opportunistic bacteria. The bacteria out there in the moisture, the mud, the manure that simply causes the infection and because these bacteria haven’t evolved to live in the udder of the cows the cows immune system responds strongly to them and is, in many instances, successful in eliminating them.

Sevie Kenyon: What does this imply for the dairy business?

Pam Ruegg: We had a lot of these culture negatives. They were about 25% of the samples. Then we found that the most common pathogens to the bacteria that we found associated with mastitis were E. coli, environmental streps, klebsiella, and then a whole host of about 17 or 18 other bacteria of which many just are present in the environment of the cow, and again, opportunistically causing these infections.

Sevie Kenyon: You also looked at some work with antibiotics. Could you describe that for us?

Pam Ruegg: For many of the bacteria we checked for resistance to commonly used antibiotics that are used on farms to treat mastitis. It doesn’t appear that there’s an emerging explosion of antibiotic resistance in these bacteria but it does appear that predictable relationships between penicillin used on dairy farms and resistance to penicillin are found on some of these farms. In other words, we don’t see an increasing trend of antibiotic resistance but there does seem to be some stable populations of resistance to some type of bugs.

Sevie Kenyon: We’ve been visiting with Pam Ruegg, Department of Dairy Science, University of Wisconsin Extension in the College of Agricultural and Life Sciences, Madison, WI and I’m Sevie Kenyon.