It should be no secret that in cow country bovine viral diarrhea (BVD) reduces productivity and increases death loss in all types and classes of cattle. But, controlling BVD is no small task.
In an effort to get a handle on BVD, the state of Colorado and Colorado State University have initiated a long-term campaign to control BVD. Jim Kennedy, DVM, director of Colorado's Rocky Ford Veterinary Diagnostic Lab, says the Colorado Voluntary BVD Program is a multi-level effort (see sidebar on page 38) designed to:
Improve reproductive performance in the state's cattle herds.
Improve pre-weaning calf performance.
Lower calf treatment costs and death loss.
Provide more marketable cattle.
“Clinical signs of BVD have obvious impacts on infected animals,” Kennedy says. “But, more devastating are those animals that don't live up to potential through lower weight gains, increased disease susceptibility and diminished reproductive performance.”
Kennedy credits the Academy of Veterinary Consultants and the American Association of Bovine Practitioners for their aggressive programs and protocols to address BVD. Key to these programs' success is the combination of testing, vaccination and biosecurity.
“Vaccinations are an integral part of any control or eradication program,” Kennedy emphasizes. “But, both groups recognize vaccination alone won't control the disease.”
The major source of BVD infection is persistently infected (PI) animals. PIs result from cows being exposed to the virus during pregnancy and the fetal calf becoming infected. Although these calves often show no signs of illness, they can shed the virus in such numbers that even well-vaccinated animals are at risk.
Kennedy also points to the practices of Lucy Rechel, Yerington, NV, owner of Snyder Livestock (BEEF magazine's 2004 Trailblazer Award winner) as an impetus for the Colorado voluntary program. Two years ago, Rechel established stringent biosecurity measures for her feedyard. Included were requirements that all cattle entering her facility test negative for BVD persistent infection (See “Getting Serious About BVD” March 1, 2003, BEEF; and “First Blood” Nov. 1, 2003, BEEF).
“Lucy's work in Nevada really got us thinking that if ranchers did some things at home to show they're eliminating PIs in their herds, cattle feeders might prefer their calves,” Kennedy explains. “It stands to reason that if you can save the feedlot costs associated with BVD, you'll have a more marketable animal.”
Assessing the economic impact
To demonstrate how expensive BVD can be in, Kennedy is working on a computer model to predict the impact of PIs in a feedyard. Research shows one PI calf in a pen can infect at least 30% of its pen mates with the BVD virus, he says. And, in a ripple effect, 20% of animals in pens on either side of the index pen can become infected.
“The effects of that one animal gradually decrease as you radiate away from the index pen,” Kennedy explains. “There's no question just one PI can have a devastating effect on a feedlot — certainly far greater than the one animal itself or even on its pen mates.”
Kennedy's preliminary work using his BVD model suggests the cost of a single PI in a feedyard may approach a mean average of $700-$800/pen for every pen in the feedyard. Kennedy points out his economic models need refining, but says there's plenty of anecdotal data to support the range of economic impacts he's finding.
Todd McMenimen, Trickle Creek Ranch, Ignacio, CO, is the first Colorado rancher to achieve certified BVD-PI-free status in the state. He's taken his Angus herd though each level of the Colorado BVD program.
“There's no question this disease is becoming identified as a culprit in a lot of disease complexes,” he says. “Were getting to the point where attention to BVD, beyond vaccination, is going to involve strict biosecurity and testing measures as a normal practice.”
McMenimen feels the program being established in Colorado offers a template for producers to ensure they have no BVD PI animals in their herd. “And, by sticking to the process as you add new animals to your herd, you can ensure your herd remains BVD-PI free,” he says.
The PI testing component
A variety of testing procedures and schemes may be implemented depending on the producer's individual goals, McMenimen explains. “If protocols are carefully established before testing begins, the additional cost to move from Level 2 to Level 3 should be minimal,” he adds.
Level 3 BVD-PI-free certification verifies that all cattle within the herd have been tested for BVD-PI status and have tested negative, with the exception of any unborn calves, which are required to be quarantined and testing immediately after birth.
To date, the most popular and cost-effective BVD diagnostic test has been the immunohistochemistry (IHC) test on a skin biopsy or ear-notch taken from an animal.
Serological tests can also be used to screen a herd for PI exposure. These tests are reported back as titers to type 1 and type 2 BVD and are performed at the Fort Collins, CO, diagnostic lab at a cost of $10/sample.
Whole blood tests utilizing polymerase chain reactions (PCR), the latest in diagnostic technology designed to detect DNA or RNA, can also be performed. By incorporating PCR technology and pooling samples, the PCR test can be quite cost effective — maybe the best method for commercial producers to reach Level 3.
The cost of the pooled PCR is about $50/pool. If a positive signal is detected, the individual animals in that pool can be retested with the ear-notch test to determine which animals are positive.
Harry Backstrom, DVM, Bayfield, CO, is a practicing veterinarian excited about the program's potential for Colorado cattle producers. He's especially impressed with its simplicity and low cost.
“This is a sensible herd health protocol that certainly will help reduce incidence of BVD and its associated health costs at the ranch,” he says. “The payoff will be when ranchers can use BVD-PI-free status as a marketing tool when dealing with feeders.
“I think once the word gets out about how uncomplicated this program can be for a commercial producer, we'll see more and more cattlemen who want to become certified as having a BVD-PI-free cow herd,” Backstrom says.
To measure your herd's BVD risk, take the quiz on page 46.
Level 1 of the Colorado Voluntary BVD Program deals with the development of a biosecurity plan that addresses the herdsmanship, record keeping and appropriate vaccination.
Level 2 incorporates strategic testing to identify problem herds with persistently infected (PI) animals. Herds completing Level 2 are considered low-risk herds and are presented with written documentation of their low-risk status. Low-risk herds should realize a marketing advantage over herds that haven't addressed potential problems BVD PI cattle will cause.
Level 3 herds have completed the requirements of Levels 1-2, individually tested all animals in the herd, and attained certified BVD PI-free status.
For more information, contact Colorado State University's Rocky Ford Veterinary Diagnostic Lab at 719/254-6382.