Bovine Leukemia Virus (BLV) is a zoonic virus that attacks the immune system of bovine (cows) and can lead to the development of bovine leukosis, lymphoma and lymphosarcoma. BLV can impact the productivity, longevity, and welfare of dairy cattle (Bartlett et al., 2014) and persists in over 94% of dairy operations in North America with an average herd prevalence of 46% (LaDronka et al. 2018). Our research project utilizes farm and cow level financial, production and biological data from four Michigan dairy farms over the span of five years to test for differences in partial profit across cows infected and not infected with BLV. Economic evaluations were based on a partial profit equation where we hold constant all revenues and costs not impacted by BLV. Each component of the partial profit equation is calculated using farm financial invoices and receipts, and production and biological data from each production year. Next, we used fixed effects regression analysis with the unbalanced panel dataset where we determined that BLV positive dairy cows had lower partial profit than BLV negative cows. Finally, through a sensitivity analysis on key partial profit input variables a range of partial profit loss for BLV positive cows was estimated to be between $198.34 and $496.76 per cow per lactation. The estimated loss in partial profit for BLV positive cows is greater when partial profit is calculated with energy corrected milk, which accounts for milk merit via fat and protein percentages, showing that BLV infection may have a greater negative impact on milk components such as fat and protein more so than total milk production. Given these estimates, for an average Michigan dairy herd of 550 cows and 46% herd BLV prevalence, we would expect an annual loss between $50,180.02 and $125,680.28 due to BLV infection.
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