The following commentary does not necessarily reflect the views of AgWeb or Farm Journal. The opinions expressed below are the author's own
Among the most insidious pathogens affecting cattle, the bovine viral diarrhea virus (BVDv) stands out. Clinical signs and effects of the disease can vary widely, and while its name includes the word “diarrhea,” the most damaging effects include abortions in cow-calf herds and the role of BVDv in the bovine respiratory disease complex in stocker and feeder cattle.
At the heart of the issue, persistently infected (PI) cattle represent a critical control point and a significant ethical and financial challenge for producers. PI cattle are those that survive infection during gestation and shed the virus for as long as they survive.
In a recent article titled “Enhanced BVDv Control Would Benefit the Cattle Industry,” Oklahoma State University Extension specialist Derrell Peel, PhD, notes that BVDv incidence is relatively low at about 0.3 percent of cattle and only about 4 percent of cow-calf herds will have a PI-positive animal. However, he says, commingling that occurs in the stocker and feedlot sectors greatly magnifies the impact of PI cattle. A single PI calf may expose at least 150-200 head of other cattle to BVDv over its life, and around 79 percent of feedlot cattle are exposed to BVDv from a small number of PI cattle.
In theory, widespread testing and removal of PI animals, coupled with effective vaccination protocols in cow-calf herds, could eradicate the BVD virus. In reality though, testing adds production costs, as does removal of a PI calf, which might appear healthy. And from the rancher’s perspective, they cover the costs while stocker and feedlot operators reap at least a portion of the benefits.
Peel notes that Oklahoma State University research shows the net value of enhanced BVDv control in the beef industry could be as much as $24 per head. Currently though, the feeder-calf market does not provide mechanisms for directly compensating cow-calf producers for their investments in BVDv control. Peel refers to this as an example of “market failure,” where market participants do not fully recognize and incorporate all costs and/or benefits into their private decisions.
Cow-calf producers can benefit from testing calves, replacement heifers and imported animals for BVDv. Test results almost always will be negative, but timely diagnosis of a PI animal can prevent substantial losses from declining pregnancy rates and calf morbidity. Benefits associated with risk reduction are, however, difficult to quantify financially. For information on how to measure those benefits, read “Analysis of cost-effectiveness of veterinary interventions,” from Dr. Bob Larson at Kansas State University.
Some marketing chains will provide premiums for calves certified as BVD-tested and PI-free, but that trend has been slow in developing. In its annual survey of value-added markets, Superior Livestock Auction has collected data on BVD-tested calves since 2008. In their data, premiums averaged $2.42 per hundredweight in 2012, $2.97 in 2013, $1.63 in 2014, $2.42 in 2015 and no advantage in 2016.
Scientists and veterinarians recognize that removal of PI calves is critical for control of BVDV, but that discussion always leads to the question of what to do with those calves. Producers facing tight margins might be reluctant to euthanize or slaughter PI calves that appear healthy, and the potential loss of revenue can even discourage some producers from testing.
Ethically, the options for producers who find PI calves include euthanasia or shipping directly to slaughter. In some cases, producers can limit their losses by isolating and feeding PI calves to slaughter weights, either on their own operations or at a finishing facility that is equipped to feed the animals in complete isolation. The option entails considerable risk as morbidity and mortality rates tend to be high in groups of PI calves.
Peel notes that an indemnity program to pay for eliminating PI animals might increase incentives for better BVDv control in cow-calf herds. In any case, an industry-wide effort with shared risks and benefits across sectors, will be needed to significantly reduce the impact of the destructive BVD virus. For more, read BVD Biosecurity, Vaccination and Diagnostics from Bovine Veterinarian.