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Use high SCC first-test results to manage mastitis

PD Editor Walt Cooley Published on 31 December 2013

Idaho veterinarian Mark Kirkpatrick recently encouraged producers who are using regular DHIA testing to harness the power of the data they are collecting to improve their dairy operations, especially to improve disease monitoring and evaluation of the impacts on milk production.

Kirkpatrick, a managing technical service veterinarian for Zoetis, spoke in December at Idaho DHIA’s annual meeting in Twin Falls, Idaho.

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“I can’t imagine running a multimillion-dollar dairy and not driving with the gauges,” Kirkpatrick said of using DHIA records and regular milk testing for management decisions.

Kirkpatrick said dairy records systems have evolved from simply tracking milk production and sire identification to powerful tools to improve reproduction, genetics and herd health.

He recommended producers first set up their systems to track health incidents in one of eight significant categories, an idea promoted by University of Minnesota’s Dr. John Fetrow.

Those categories include milk fever (MF), retained placenta (RP), displaced abomasum (DA), metritis (MET), ketosis (KET), mastitis (MAST), lameness (LAME) and pneumonia (PNEU).

Kirkpatrick said some dairymen tell him they don’t want to track all of the categories because not all of the conditions may be treated with a therapeutic drug protocol.

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Conditions such as milk fever and retained placenta are typically not treated with an antibiotic, yet they are potential indicators of possible immune system depression. Kirkpatrick urged producers to use record-keeping more broadly.

“Think of your record system not as being just an insurance policy and keeping track of therapeutic use,” Kirkpatrick said. “What are the outcomes that you could learn from your records? Think beyond just residue tracking.”

Tracking all eight categories and communicating the percentage of incident rates recorded to the herd’s veterinarian, nutritionist and owner or herdsman can set a baseline for herd health and become a diagnostic tool for the dairy’s management team, Kirkpatrick said.

Tracking somatic cell count (SCC) scores at first milk test can be one such diagnostic tool. Kirkpatrick displayed first-test SCC data from 22 Pacific Northwest herds and 164,000-plus cows. To be included, all herds had to be recording disease protocols and were performing routine monthly DHIA testing.

As a baseline, Kirkpatrick examined the effect of having a clinical mastitis case in the first 60 days of lactation. Across all lactation groups, the impact was a reduction of approximately 5 pounds of milk production per day through 240 days of lactation.

In comparison, cattle that had a high first-test SCC score (more than 200,000 SCC) tended to double the production losses to approximately 10 pounds per day, with losses extending to 210 days of lactation. The impact of a high first-test SCC had associations in other areas.

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Cows that had the condition tended to leave the herd 64 days earlier than their unaffected counterparts. Of all the cows that developed a clinical case of mastitis, those with a first-test high SCC had a case 57 days earlier.

The risk of clinical mastitis is a serious concern. “As an industry, we tend to focus on the cost of therapy and milk discard for the case, but the mastitis created erosion of the lactation curve for these cows is the big, big cost,” Kirkpatrick said. “It’s the cost of the milk that we didn’t produce.”

His data analysis also showed that high first-test SCC cows were almost one reproductive cycle behind herd counterparts (18 days).

Kirkpatrick said the risks for high SCC first-test cows are multiple, including milk production losses, increased risk of clinical mastitis, additional cost of treatment, decreased chances of successful cure when treated, decreased reproductive efficiency and increased involuntary culling.

“I believe high somatic cell counts at first test are as much a serious disease condition as clinical mastitis at any time. First-test somatic cell counts are both an objective and repeatable indicator of fresh cow udder health, as compared to the subjective identification of clinical mastitis.” Kirkpatrick said.

Kirkpatrick recommended producers track first-test SCC cows on a monthly basis. He suggested tracking the percentage of the herd with more than 200,000 SCC at first test. His targets for test results would be to achieve fewer than 10 percent of each month’s calvings affected with a high first test somatic cell count.

If elevations occur, the management team should examine the dry, close-up and fresh pen housing to look for environmental risks. Additionally, cows going dry should be dry treated with a dry cow tube to help treat existing subclinical infections, and infused with an internal teat sealant, to help prevent development of new mastitis infections.

The National Mastitis Council suggests that a somatic cell count of more than 200,000 is indicative of a subclinical mastitis case.

He also suggested using two sequential DHIA test-day somatic cell counts, which will allow dairy management to classify the herd into four segments of non-infected, new infections, cures and chronics. Two consecutive low SCC scores (below 200,000) would be cows considered to be non-infected with subclinical mastitis.

Two scores above 200,000 would classify the cow as chronically infected. A metric to focus on are the cows that have a previous test of less than 200,000 followed by the next test going above 200,000. These individuals should be categorized as new infections.

A target for this area would be to hold this percentage to 8 percent or lower. Kirkpatrick suggested keeping a running track of the percentages of cows in each of these categories by test month and lactation group.

“High somatic cell counts at first test should be considered a real disease condition, rather than just a number. The only way we can detect it is through routine testing,” Kirkpatrick said. PD

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Walt Cooley
Editor
Progressive Dairyman

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