20 February 2013

3 minute read

By identifying and counting three different primary leukocytes, the test indicates whether the cow has mastitis before the onset of visible symptoms.

The white blood cell analysis is called the Milk Leukocyte differential (MLD) and has economic implications as farmers will be able to target only infected cows with antibiotics and not all cows at dry off.

Selective dry-cow therapy has been shown to have economic benefits, but it hasn’t been a practical option because currently available testing methods are either costly and time-consuming or they lack accuracy,” explained Mitchell Hockett, PhD, director of technical research for Advanced Animal Diagnostics (AAD) and the principal investigator of the study.

“This study shows the MLD reliably diagnoses subclinical mastitis and effectively guides selective treatment decisions at dry-off.”

The test equipment consists of a reusable milk collector, a dispoable diagnostic slige and a reader, a fluorescent imaging system housed in a tabletop unit that requires less space than a traditional computer.

Marketed as Qscout TM MLD the trial results were presented recently at the National Mastitis Council’s annual San Diego meeting.

The trials commenced by collecting quarter milk samples within 24 hours of dry-off from 300 Holstein cows that were around 223 days in gestation. Investigators then screened the samples using the MLD; they also obtained somatic cell counts and bacterial cultures.

Half the cows in the study were randomly assigned to a traditional treatment group and had all four quarters dry-treated with the antibiotic cephapirin benzathine. The remaining cows were assigned to a selective group, and only those that tested positive for subclinical mastitis in at least one quarter were treated in all four quarters. All cows in the study then had their teats sealed with an internal sealant and treated with a barrier dip.

Ten days after calving (on day 10), investigators collected quarter milk samples for culture.

At 24 hours prior to dry-off and 10 days after calving, the rate of quarter-level infection as determined by culture did not differ significantly between the traditional and selective groups. On day 10, the rate of infection was numerically lower in the selective group.

“We undertook this dry-cow study to put our MLD technology to a tough test,” said Joy Parr Drach, AAD’s president and CEO. “Untreated subclinical disease at dry-off puts a cow at significantly higher risk for developing clinical mastitis later on, so accurate diagnosis is essential to successful selective treatment.”

She added, “The results of this study reinforce the diagnostic accuracy of the MLD. It shows that Qscout MLD can help producers use antibiotics judiciously at this critical stage of lactation — and realize the economic benefits of selective treatment — without increasing infection rates post-calving.”

Use of the test requires elementary training. Units are expected to become available this year. 

For more information, call (855) 722 6868 or (855) Q2count or visit www.advancedanimaldiagnostics.com