January 2015

DHI NEWSMichigan • Wisconsin • Indiana • Ohio

“Enhancing producer profitability through integrated services.”

Time to Reconsider Bovine Leukosis Virus

Every time we try closing the book on bovine leukosis virus (BLV), additional research adds a few

more chapters. One of the most beneficial has been development of a way to establish a BLV herd profile, which helps evaluate disease impact on milk production and cow longevity. Considering the high prevalence of disease in the U.S. (on average, 40 to 45 percent of cows in a herd), the BLV herd profile can be an effective tool to monitor BLV prevalence and have a positive impact on dairies. Any size dairy can use their DHI milk samples to establish a profile for BLV. To do this, simply have milk samples from 40 cows collected during routine DHI testing analyzed for BLV. Cows to be tested should be herd-

raised or have been in the herd two or more years. The samples should also include ten cows from each lactation group (1st, 2nd, 3rd, ≥4th). BLV profile results, and the associated impact on production are shown in the table.

Research from Michigan State University and AntelBio1 shows that for every percentage increase in BLV profile, the rolling herd average for milk production decreases by 24.2 pounds. Therefore, a herd with a BLV profile of 75 percent, which is not uncommon, is losing 1,210 pounds of RHA milk per cow compared to herds with a BLV profile of 25 percent. The impact on milk production is partially explained by the effect of BLV infection on longevity. In the same study, data shows that BLV positive cows were 23 percent more likely to leave the herd within one and a half years of a positive BLV result than test-negative cows. With fewer cows surviving to the most productive years of their life, overall herd production is reduced. Although it has been difficult to identify the underlying cause of BLV’s effect on longevity, a reduction in immune function has been implicated. Unable to generate a normal immune response, BLV infected cows are more vulnerable to the impact of otherwise inconsequential infections, and are therefore more likely to be culled for health reasons, even if the reason isn’t directly BLV. The BLV profile also helps focus disease control efforts by illuminating when infection is predominantly transmitted. By selectively testing animals from different lactation

groups, herds can see when transmission is taking place. For example, a herd with an overall prevalence of 75 percent may realize that 50 percent of their first lactation cows

are already infected, leaving only 25 percent to become positive as a result of routine cow management and environmental conditions. The BLV profile is a cost-effective testing protocol on DHI samples which determines the prevalence and impact of BLV infection on milk production in any size dairy. Used on a regular basis (every 6 to 12 months), the testing protocol can assess the value of BLV control programs by measuring changes in BLV prevalence and associated changes in RHA and cow longevity. To learn more about submitting samples to establish a BLV profile for your herd, talk to your NorthStar Specialist or call AntelBio at 800.631.3510.

Number Current 87 75 62 50 37 25 12 0Positive BLV Profile

40 100 290 615 896 1,210 1,500 1,815 2,105 2,42035 87 290 615 896 1,210 1,500 1,815 2,10530 75 290 615 896 1,210 1,500 1,81525 62 290 615 896 1,210 1,50020 50 290 615 896 1,21015 37 290 615 89610 25 290 615 5 12 290 0 0

Expected RHA Improvement (lbs) with BLV Profile Improvement Target BLV Profile

RHA improvement (lbs)

Establishing Your BLV Index

Select Animals:

• 40 cows total

• All herd-raised or 2+ year herdmates

• 10 each from 1st, 2nd, 3rd, & ≥4th

lactation

• Determine Profile: Percent positive

of 40 samples

• Calculate Impact: (Current Profile –

Target Profile)× 24.2 lbs RHA

• Monitor Progress: Resample every

6-12 months

1Bartlett PC, Sordillo LM, Byrem TM, Norby B, Grooms DL, Swenson CL, Zalucha J, Erskine RJ. 2014. Options for the control of bovine leukemia virus in dairy cattle. J Am Vet Med Assoc. 244(8): 914-22.

NorthStar Cooperative: 1.800.631.3510 • Michigan ULS Lab: 1.800.836.8114 • Wisconsin Lab: 1.800.436.9344 • northstarcooperative.com

Change in PCDART WorkshopsTo better serve our customers, NorthStar is restructuring our formal Spring PCDART Producer Workshops. We will not have formal meetings this year, which allows us more time to set up one-on-one meetings to meet your dairy’s

training needs. NorthStar’s PCDART Support Specialists can customize training and provide on-farm sessions for your dairy. If you would like to schedule a session, please contact the NorthStar office at 800.631.3510.

USING 21ST CENTURY TOOLSUnlike culture, DNA TESTING provides:Speed Identifies all organisms in as little as 24 hours.

Improved Detection Superior sensitivity, detects dead & dying organisms that yield ‘no growth.’

MASTITISDETECTION

Milk Diagnostic testsTest Days/ Results Price Pregnancy 1 $4.50Contagious 3 Mastitis 2 $27.00Complete 16 Mastitis 3 $35.00Leukosis 5 $6.00 Bulk Tank 5 $18.00

Ask for any of these

options on your DHI

test day.Test Days/ Results Price

BVD 5 $6.00 Pooled (250:1) 10 – 20 $40.00

Johne’s 5 $6.00 Bulk Tank 10 $40.00Neospora 5 $6.00

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