BVDV assessment tool. Kansas State University College of Veterinary Medicine offers a risk analysis tool on their Web site. It consists of a simple questionnaire where you provide answers for your herd, and then it calculates your risk, which can take several minutes. In addition to the risk assessment, the results show probability of costs for prevention and losses due to BVDV exceeding the stated dollar figure given with the results. It identifies a "best choice” strategy for including in a BVDV control plan.
Want to read more about Tom Hougen's experience? Click here to download a pdf of his presentation from the 2009 U.S. BVDV Symposium that took place in Phoenix in January.
Looking through a group of cattle, could you identify those that are infected with bovine viral diarrhea virus (BVDV)? Chances are you can't.
BVDV is adisease with multiple clinical symptoms. There are three broad types of the disease (see sidebar). BVDV has been characterized as a stealth disease because it lurks in your cattle herd and causes incremental losses that add up over time. At the U.S. BVDV Symposium in Phoenix, Ariz., in January, ranchers described how the disease resulted in reproductive losses, lower production efficiency and calf losses.
One rancher, Tom Hougen, owner of Hougen Ranch in Montana, said he didn't fully understand the disease when he started noticing spikes in production losses. He first learned about BVDV at a producer meeting in January 2003. Just a few months prior to the meeting, his ranch had an increase in sick calves and unexplained abortions in bred heifers. Then, that spring, there was an increase in death loss on calves.
At that point, Hougen remembered the PI (persistent infection) calf he saw at the producer meeting and contacted his veterinarian. The herd was tested and BVDV was confirmed.
"In 2004 we developed a timeline to rid BVDV from the herd,” Hougen says. That involved vaccinating with a modified live vaccine and testing open replacement heifers, purchased animals and suspect animals. "Cows do not need to be screened unless they have positive PI calves,” he says.
Cost versus benefits seems to be the biggest hurdle for many producers to overcome in developing a BVDV control plan. Testing and vaccination costs, however, can be paid back in improved
reproduction, overall herd health and increased gains.
The real cost.
A 10-year profitability model from veterinarian Robert Larson at Kansas State University (KSU) estimates the cost of PI cattle at $14.85 to $24.84 per cow per year exposed to a bull. In the feedyard, PI exposure can cost $41.84 to $93.52 per animal.
To start, conduct a BVDV risk analysis. Producers can analyze their risk with KSU College of Veterinary Medicine's online risk analysis tool. Complete a simple questionnaire and the results will show the estimated losses due to BVDV and costs of prevention. The tool also identifies a "best choice” strategy in a BVDV control plan.
Develop a control plan.
Michigan State University veterinarian Dan Grooms suggests including the following elements in your plan:
- Biosecurity. Identify and eliminate PI animals. Various PI tests involve blood samples, ear notches and skin samples.
- Improve herd immunity. There are 150 different BVDV vaccine combinations, both modified live and killed. Work with your veterinarian to determine your strategy. "Remember, vaccination is a tool, not a silver bullet,” Grooms says. BT
Also referred to as "primary BVDV” and "transient BVDV” infections. Subclinical infections often go unnoticed. Severe acute infections can impair the immune system, which allows for secondary
infections to occur, says Dan Grooms, Michigan State University veterinarian.
This type of infection occurs when a preg-nant dam becomes acutely infected with BVDV or when a persistently infected cow becomes pregnant, Grooms says. The result on the calf depends on the severity of the virus and the stage of gestation when the infection occurs.
Persistent infection (PI)
PI occurs when the fetus is exposed to the virus between 50 and 125 days of gestation and survives, Grooms says. The calf becomes a lifelong carrier of the virus and will shed the virus even though it may show few symptoms or just be considered a "poor doer.”
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