Mastitis is the most common disease affecting dairy cattle. “Preventing mastitis is certainly important but identifying it is equally important,” said Ernest Hovingh, DVM/PhD, a highly visible presence at ag gatherings, he averages about 100 presentations a year, often more. His original topic at the 2015 Lebanon Dairy & Crops Compliance Day was ‘Objectively Investigating Milk Quality Issues’, but mastitis took front and center. After identifying mastitis, he says, “it must be properly managed.” Hovingh opened with a Socratic questioning method, wanting to know from attendees if they could tell from varied slides “whether or not this cow has mastitis”; if not, what could it be?
The slide in question showed a cow with an obviously distended udder. Mastitis, he said, “is basically inflammation. That’s what ‘itis’ means, whether it’s arthritis in the joints or laryngitis that swells the larynx. With mastitis, the udder has inflammation.” He said that the vast majority of the time, a bacterium is responsible for this bovine discomfort. Which of the cows will have clinical signs of mastitis (flakes, clots, watery milk, etc.)? When diagnosing mastitis, signs of inflammation are heat, pain, swelling of udder, a change in appearance of milk, an increase in the electrical conductivity, an increase in milk temperature and also in the somatic cell count. “Some of these are clinical, things you can actually see with your eyes,” Hovingh says. “Some you will not see because not each of these shows up in every inflammation. You can have a cow with mastitis that only has an increase in somatic cell count but doesn’t have other symptoms.”
In diagnosing the disorder, PCR [Polymerase Chain Reaction] is a technique used to amplify a single or few copies of a piece of DNA across several orders of magnitude, generating millions or more copies of a particular DNA sequence. “We can be very specific with 15 different pathogens,” said Jere High, Executive Director of Lancaster County DHIA. “It doesn’t matter if the milk is treated or not. Nor does it have to be a sterile sample. Someone can take it right out of a D jar milk sample.” High went on to say that milk inspectors can pull a sterile bulb tank sample and give results if there is anything contagious, like staph-aureus, strep-ag or mycoplasma. “With the one test they use, it can show all kinds of environmental issues, or contagious pathogens. The in-depth ability with DNA testing allows some leeway: it doesn’t matter if the organism is dead or alive.” Hovingh said, “Instead of taking bacteria in the lab and actually growing it, it takes the milk sample, puts it through this equipment, and hooks the genetic material of the bacteria.”
“We still do standard cultures because they are easy to do,” High said. “But with the DNA testing we basically strip out DNA in the sample of milk that we are given, and we look for these 15 specific pathogens. Also it allows us to know if that cow is penicillin-resistant.” You can also select your high SCC cows after they have been tested in the Lancaster DHIA lab.
A preventative, sound milking routine is imperative. Goals to strive for are not always easy to attain but if you have a high percentage of implementing the following suggestions, you’ll be ahead of the game. Ideally, you will have calm cows that enter the parlor willingly; a milking unit attached to clean, dry, well stimulated teats; prompt initiation of a rapid milk flow; complete milk-out with abrupt drop in flow; prompt removal of milking units; and a prompt release of post-dipped cow into a clean environment. “You don’t really need sticks to chase cows into the parlor,” says Hovingh. “Udder preparation” calls for what Hovingh describes as ”Non-negotiable steps”: Dry-wipe if necessary to remove (excessive) crud; Milk must be stripped from each quarter (at least 3-4 squirts per teat); Pre-dip contact time of 20-30 seconds on (mostly) clean teat; and Milking unit applied 60-90 seconds (or more, but not less) after start of prep routine. Goals of a good milking routine include: a calm cow that enters the parlor willingly; a milking unit attached to clean, dry, well stimulated teats; prompt initiation of rapid milk flow; complete milkout with abrupt drop in flow; prompt removal of milking unit; prompt release of post-dipped cow into a clean teat; and Milking unit applied 60-90 seconds (or more, but not less) after start of prep routine.
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PCR-based mastitis DNA testing leads to more effective treatments by:
- Specifically identifying coliforms
- Identifying sources of mastitis in a single cow or bulk tank sample
- Identifying sources of mastitis in cows already being treated
- Decreasing test time from 2-10 days (conventional culturing) to 1-2 days from when we receive the sample at the lab
- Finding sub-clinical cases before they become clinical or chronic