QScout Farm Lab Diagnoses Subclinical Mastitis

QScout Farm Lab Diagnoses Subclinical Mastitis

First-calf heifers at Son-Bow Farms were having somatic cell counts (SCC) above 200,000 too often.
Worse, these heifers produced on average 6 lb. of milk less than herd mates with lower cell counts. Over the course of the lactation, that often tallied up to 1,800 lb. less milk, says John Freund, dairy manager at the 1,000-cow Maiden Rock, Wis., dairy.

But the question always remained: What to do about it?

A year ago, Freund found what he hoped to be the answer. He started testing milk from each quarter of each fresh heifer with QScout MLD (milk leukocyte differential) test, which is designed to identify and differentiate white blood cells. The MLD test is conducted with the QScout Farm Lab, which uses fluorescent imaging to differentiate macrophages, neutrophils and lymphocytes.

By using an algorithm of the cell types, percentages and total counts of each type, the QScout Farm Lab
estimates whether a quarter is subclinically infected.

On fresh heifers, Freund tests all heifers that are seven to 13 days in milk. (Testing earlier than that has been found to be wasted effort since a high proportion of infected quarters self-cure right after calving.)
If QScout flags a quarter as positive, Freund treats that quarter. “With QScout, we’re finding a greater percentage of quarters positive than with DHI test greater than log score 4 (200,000 SCC),” he says. The conventional SCC DHIA test, which is a composite of all four quarters, was showing about 20% of heifers positivie. The QScout, which reads each quarter, is finding about 25% positive.

“We’ve been seeing a nice response to treatment,” Freund says. An added benefit: Reproduction has improved.  

Freund also uses the QScout test at the end of lactation. He screens cows with a single SCC test greater than 400,000 or two SCC tests above 300,000 cells per ml. If they flag positive on the QScout, he treats positive quarters with a lactation tube for two days. Then, he dries off the cow normally, dry treating all four quarters.

“We think this is really cost effective because we are getting 93% dry cow cures,” he says. “The industry benchmark is closer to 80%.”

The QScout Farm Lab doesn’t come cheap, though. The current price is $18,000, and each test slide is $5. But the unit will automatically load and read up to 20 slides at a time and provide results in about an hour, says Mitch Hockett, director of external research and technical marketing for Advanced Animal Diagnostics, the developer of QScout.

There is also no guess work when reading the slides. Red means an infected quarter; green, not infected. The unit also provides computerized action reports. Smartphone apps are planned for the future.
Some dairy producers are using QScout to selectively treat dry cows, infusing only those quarters that trigger a positive QScout reading, Hockett says.

Others are also using QScout when a cow flares up with clinical mastitis. They will check all quarters and treat those that are reading positive since they have to discard milk anyway.


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