Eradication of this virus is difficult as PI calves often survive while appearing to be fully healthy. When PI calves enter production channels they shed enormous numbers of virus particles - up to 10 million particles daily - infecting otherwise healthy cattle. PI cattle are the main source for transmission and spread of BVD.

The managers of the Montana BVD-PI Herd Screening Project believe there may be added incentive beyond better herd health for ranchers who identify “PI negative” calves. They simply may be worth more money come marketing time.

“We think calves screened as PI-negative deserve at least a 4¢ per pound price advantage over unscreened calves,” says Clint Peck, Montana’s director of Beef Quality Assurance. “PI-negative status says the animals are not persistently infected with the BVD virus and greatly reduces the risk of spreading the disease throughout the production chain.”  The main negative health effect of BVD is it can inhibit conception and/or cause abortion in susceptible females. It also suppresses the immune system, making infected animals more susceptible to other diseases.

The costs and impacts of the BVD virus can escalate once calves leave the ranch and end up in a feedlot, says Dr. John Paterson, Extension Beef Specialist at Montana State University. “The BVD-PI calf that exposes its feedlot pen mates to massive amounts of BVD virus on a daily basis creates economic chaos for the feedlot operator,” Paterson says. “Feedyard research in Kansas indicates there's a $47 per head cost for every animal going into the feedyard because of PI exposure.”

One bad apple, they say, can spoil the whole bunch. That wisdom certainly holds true for calves or feeder cattle commingled for back-grounding or finishing, where one animal persistently infected with BVD endangers the health, performance and profitability of the entire group.

PI calves, remember, are carrier animals, infected early in gestation. Some survive through weaning, appear perfectly healthy and subsequently spread the BVD virus through herds and feedlot pens with great efficiency.

Improved testing methods and growing awareness of the economic impact of BVD are prompting some stocker operators and feedyards to initiate broad testing programs and remove PI cattle at the earliest opportunity.

Health benefits
Mark McDaniel is a cow-calf and stocker operator near Caney in southeastern Kansas who is convinced of the value of BVD testing. He regularly purchases put-together groups of sale-barn calves for his grazing operation and retains ownership through finishing. He sends lightweight calves to a backgrounding lot operated by Bill and Dianna Helm, near Nowata, Okla., for a 30-day preconditioning period before placing them on grass. Heavier groups go straight to grass, and he preconditions calves from his own cow herd on the ranch. All the calves eventually go to Premier Cattle Co., a feedyard near Syracuse, Kan., where he retains ownership through finishing.

McDaniel says the Helms have PI tested all the cattle coming into their backgrounding lot for some time, and he noted significant improvements in the health of calves he sent there. Preconditioning costs dropped by $6 to $8 per head, and the benefits continued through the grazing period on the ranch. “We’re just not seeing the chronics, and death loss is way down.” Veterinary bills have been about two-thirds lower than in the past, he says. Recently, he began PI testing all the calves he purchases and calves born on the ranch. If a calf from his own herd tests positive, he tests its dam.

At the backgrounding facility, Bill Helm says he purchases 150 to 200 cattle per week from area sale barns. The Helms background some cattle for clients along with those they purchase. Depending on the season and type of cattle, they retain ownership on some through grazing and feeding, and sell others to stocker operators or feeders. Testing and removing PI calves, he says, has noticeably improved health and performance through each production stage.

McDaniel says he just recently began sending the first groups of “PI-free” cattle to the feedyard and has not been able to evaluate health and performance at that stage, but he expects good results. He points out that he owns most of the calves for a long time??—??as much as 160 days on the ranch before shipping them to the feedyard??—??so the savings from good health add up.

Shaun Sweiger, a consulting veterinarian from Edmond, Okla., conducts BVD research and processes PI tests with a typical turnaround time of 12 hours or less at Cattle Stats LLC in Oklahoma City. Time is of the essence, he says. Clients, including McDaniel and Helm, take ear-notch samples as they process cattle upon arrival and send them overnight. “We want to get them the results the same day the samples arrive, so they can pull any PI calves first thing the next morning.”

For commingled sale-barn calves, Sweiger uses the individual ear-notch test, rather than pooled samples. The individual tests cost $3.75 per head. Pooled testing that combines samples from up to 100 cattle can save some money up front, but a positive result requires further individual testing to find the PI animals that caused it. Sweiger says PI prevalence in the cattle his stocker clients purchase runs about one in every two loads, making it most cost-effective to test them all right from the start.

Economic impact
Research has shown that PI cattle cause significant losses in a feedyard setting, and Sweiger is collecting data to evaluate the economic impact in stocker operations. During 2003 and 2004, a group of researchers conducted two trials at Cattle Empire LLC feedyard of Santana, Kan. The first trial compared close-out performance for pens including PI cattle to non-PI pens. Trial 2 evaluated starter-yard performance comparing differing PI exposure levels. The researchers found that the presence of a PI animal reduced overall profitability of the pen by an average of $47.43 per head. In trial 2, the cost in the exposed population averaged $67.49 per head, and the cost for the total population was $41.17.

Sweiger says grazing cattle, in a less concentrated setting, probably have less exposure to the virus compared with a similar population in a feedyard. But, he adds, BVD does account for significant health problems in stocker cattle.

“My stocker clients who test and remove PI calves see a big difference in animal health,” Sweiger says. “They have fewer sick pulls and don’t have the lingering pulls they see otherwise.” Several of his clients are getting at least a four- or five-to-one return on their testing due to lower medicine costs and lower death loss. Some also are receiving significant premiums from buyers at sale time.

Premiums at sale
Some buyers recognize the value of “PI-free” cattle, Sweiger says, while others do not fully understand the benefits. He provides his cow-calf and stocker clients with information about PI testing and its economic benefits, which they can announce to buyers at auction time. “We have seen premiums averaging from $3 to $7 per hundredweight for groups of cattle certified as PI-free, with some ranging over $10 above the price for similar cattle.”

Helm says he is sold on PI testing based on improved animal health and performance, but he has not seen much benefit in sale prices. There should be a premium, he says, but too many buyers do not understand the economic impact of PI calves or recognize the value of PI-free cattle.

The PI dilemma
Testing and removal of PI animals clearly offers benefits, but owners face the dilemma of what to do with the animal that turns up positive. It’s an ethical issue first, McDaniel says. Placing the animal back in the marketing chain allows it to spread the disease. Even cattle identified as PI and sold for slaughter could end up in someone’s breeding herd or feedlot pen.

It also is a financial issue. Owners can euthanize PI calves, but they take a total loss on the animals. Sending lightweight cattle for slaughter at salvage prices sacrifices significant profit potential.

Several of Sweiger’s cow-calf and stocker clients have been holding PI cattle in quarantined areas, trying to decide what to do with them. He says it is feasible for a feedyard to finish PI animals in isolation and to maintain effective biosecurity. Logistics and recordkeeping become a challenge as a pen of PI cattle could represent multiple owners and a wide range of weights and types.

To address this issue, Sweiger has organized a focus group, including representatives from different industry segments, with the goal of developing strategies for capturing some value from PI cattle while removing them from the rest of the pop-ulation. Sweiger stresses that BVD does not pose a threat to food safety or human health, and the dilemma of what to do with PI cattle relates only to animal health and economics.

Helm says he finishes his PI calves on his own operation in a pen positioned to avoid physical contact with other animals, and he says health and performance in the PI pen has been good. “We’re not as efficient as a commercial feedyard, but we can capture some value by feeding them.” He sells the finished PI cattle to a local slaughter facility. Removing PI animals would pay off in health benefits alone, even if he took a total loss on those cattle, he says. But generating some return by finishing them makes economic sense.

In the long term, Sweiger says the industry needs to address BVD at the cow-calf level, where a comprehensive approach using surveillance, testing, biosecurity and vaccination can dramat-ically reduce or even eliminate the incidence of PI calves. But for now, PI calves are entering the production system, forcing the need for testing at later stages. Stockers and feeders find testing to be cost-effective, but purchasing calves certified as BVD-free, even at premium prices, could be even more so.