Unseen but Costly: The Hidden Economic Toll of BLV in U.S. Dairy Herds

In the ever-evolving landscape of dairy farming, producers face constant challenges to maintain herd health and profitability. Yet, one of the most pervasive and costly threats remains largely invisible: Bovine Leukemia Virus (BLV).

Recent data shows that BLV is present in more than 83% of U.S. dairy herds, and its impact is far from benign¹. Although most infected cows appear healthy, research confirms that BLV-positive herds experience measurable losses across multiple fronts — from milk production to reproduction and herd longevity.

The Cost of BLV: By the Numbers

While BLV often goes unnoticed, the data shows that its economic toll is anything but invisible:

Milk Production Losses

• According to the USDA National Animal Health Monitoring System (NAHMS), BLV-positive herds produce approximately 480 lbs less milk per cow annually compared to BLV-negative herds².
• Cows with high BLV proviral loads can lose up to 853 lbs of milk per lactation, as shown in studies linking proviral load levels to decreased milk yield³.
• A study of 103 herds found that for every 10% increase in BLV prevalence, there is a loss of 540 lbs in rolling herd average milk per cow⁴.

Reproductive Impacts

• Cows with high BLV proviral load show a 13-day delay in days in milk to first insemination (DIM-FI)³.
• BLV-positive cows stay open for an average of 48 additional days, with each day open costing approximately $3.00 per cow, leading to $144/year in added costs per animal⁵.

Increased Culling Rates

• BLV-positive cows are 30% more likely to be culled or die within 29 months compared to their BLV-negative herdmates⁶.

Early culling increases replacement costs and disrupts productivity and genetic planning — adding a substantial hidden cost of infection.

How It Spreads

Transmission occurs primarily through blood transfer, and can happen during routine activities such as dehorning, vaccinations, calving and veterinary procedures. During these procedures and others, needle reuse between animals is a major documented route of BLV transmission on dairy farms.⁷

The Takeaway

For too long, BLV has silently eroded dairy productivity. It spreads unnoticed, while hidden losses accumulate in milk yield, reproductive efficiency, and herd longevity. Dairy farmers can work with their veterinarian to install herd health protocols that protect their herds from this invisible, yet costly, threat. 

This is the first of a three-part series spotlighting the true cost of BLV and the risks it poses to dairy operations. Our next feature will explore evidence-based prevention strategies to reduce BLV transmission — helping farmers build healthier, more resilient, and more profitable herds.

Sources

1. USDA. (2008). Dairy 2007: Part III: Reference of Dairy Cattle Health and Management Practices in the United States, 2007.
2. Bartlett, P. et al. (2014). Bovine leukemia virus and the U.S. dairy industry.
3. Nekouei, O. et al. (2016). Association between the proviral load of bovine leukemia virus and milk production in dairy cows.
4. Thompson, N. M., Kelton, D. F., & Erskine, R. J. (2019). BLV prevalence and its impact on milk production.
5. De Vries, A. (2006). Economic value of pregnancy in dairy cattle.
6. Benitez, O. J. et al. (2022). BLV-positive cows have higher mortality and culling risk: longitudinal cohort study.
7. H C Hutchinson et al. (2020) Herd management practices associated with bovine leukemia virus incidence rate in Michigan dairy farms.