New BVD-PI rule at 2008 NWSS
December 3, 2007
Bovine viral diarrhea (BVD) is a disease that usually infects cattle, but most even-toed ungulates are capable of contracting the disease. It is estimated to cost the U.S. beef industry two billion dollars each year. Some livestock with BVD may show no signs of the disease at all. Most will present mild to moderate symptoms. The degree of severity varies greatly. Infected animals may appear depressed, have a suppressed appetite, rapid breathing, snotty nose, tearing eyes, lowered milk production, fever, and diarrhea. In extremely severe cases, the BVD animals may have a fever greater than 107 degrees F and develop oral ulcers and lesions at both the coronary band and the split of the hoof.
Irrespective of the BVD case’s severity, a lowered immunity in the infected animals tends to be the biggest problem. The BVD infected animals are readily susceptible to other diseases that they may have been able to fend off otherwise. These secondary diseases become very costly to treat and may prove fatal to livestock.
The BVD virus is considered to be a transplacental disease, meaning that a pregnant mother can pass it onto their fetus through the placental wall. If a pregnant cow is exposed to the BVD virus when she is more than 125 days into gestation, the fetus may be aborted or mummified. If the viral exposure occurs between day 45 and day 125 of gestation, the fetus accepts the BVD virus as a normal part of its system. The calf is born showing no signs of the disease; however, they become a constant reservoir of the BVD virus, spreading the disease throughout their life. This condition is referred to as bovine viral diarrhea ” persistently infected (BVD-PI). Considering the mechanism for transmittal causing BVD-PI, if a calf is PI negative it will remain negative, even if it does contract the BVD virus and become sick from it at some future point. Likewise, a positive BVD-PI animal is always positive.
Kansas research suggests that the presence of one BVD-PI animal in a herd of cows will cost the producer between $14 and $24 per cow each year, in lost reproductive efficiency alone. On the feedlot side, Texas scientists have shown that exposure to one BVD-PI calf will increase health costs for every calf in the same pen or an adjoining pen by 43 percent. Data coming out of the Montana BVD-PI screening project suggests that the elimination of BVD-PI cattle in your herd is equivalent to receiving a four cent per pound premium.
The National Western Stock Show (NWSS) has taken a lead step in trying to protect the health of America’s livestock and reduce BVD exposures. Beginning with the 2008 NWSS, all cattle, bison, yak, and camelids that enter the NWSS grounds will be required to have a negative BVD-PI test. This rule is effective for all animals in these four categories, regardless of whether they are being brought to the NWSS for show, sale, or display.
The tests will have to be completed and negative documentation reported, prior to the animals being allowed onto the grounds. The NWSS has stated that no BVD-PI testing will be allowed or performed on any animal while it is on the grounds.
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Several testing mechanisms are being considered as acceptable means to evaluate for the disease. They are immunohistochemistry (IHC) via skin; antigen-capture ELISA via serum or skin; polymerase chain reaction (PCR) via skin, blood, or serum; and virus isolation. The tests can be conducted on an individual animal or through pooled sampling methodology. However, if using pooled samples, the individual animal identifications of the pooled animals must be maintained and documented. Check the NWSS premium book for more detailed information.
Michael Fisher can be reached at the Yuma County Extension office, (970) 332-4151 or by e-mail at firstname.lastname@example.org.