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BVD prevention is key to cutting costs"If you have one PI on your farm, it is costing you money," said Bruce Hoffman, president of Animal Profiling International, Inc.
By Jennifer Bremer Bovine virus diarrhea is a complex disease that can lead to a wide array of problems, both mild and severe. Identifying persistently infected animals within the herd can help prevent these problems. Bruce Hoffman, president of Animal Profiling International, Inc. discussed the importance of testing beef cattle, during a session at the 2008 Iowa Cattlemen's Association annual convention held in Ames recently. "The cost of having one PI in a herd can be an average of $14 to $24 per head per year in medication and treatment," said Hoffman. Persistently infected animals cause problems BVD can be in your herd through an acute or routine infection when the animal comes in contact with the virus within the field. Clinical signs are usually mild or nonexistent, but animals may have a fever, lower feed intake, mild diarrhea and lowered milk production. The primary way in which BVD survives in a cowherd is through the production of PI animals. These PI animals serve as carriers and remain infected for life. PI animals constantly spread the virus to other animals through the urine, feces, blood, saliva and discharges from their eyes and nose. PI animals are produced when the virus infects the pregnant female and then reaches the developing fetus prior to day 130 of gestation. Hoffman said calves have added value when tested negative for BVD. Seedstock producers, especially, should test their animals for their BVD status and insist on knowing test results when purchasing breeding stock. Feedlots have problems with PIs, also, with a $30 to $47 cost per head in treatments and a higher death loss. Persistently infected animals are twice as likely to die due to health complications. "Because of the problems PIs cause, more and more shows and fairs are requiring animals be tested negative for BVD prior to exhibition," said Hoffman. "The National Western Stock Show in Denver is one of those that require a negative test." Removal of PIs from herd Hoffman said it is very important for producers to understand the damages a PI animal can do and commit to getting rid of them in the herd. Carriers of the disease can cause sickness, reproduction losses and immune suppression. These carriers will constantly transmit the BVD virus. Getting rid of PIs should be done by humane euthanization. The American Association of Bovine Practitioners and Academy of Veterinary Consultants recommend that the animal not be sold, therefore preventing further exposure to other animals. A statement from the two organizations said, "It is widely recognized that a PI animal is defective and once confirmed, the PI status should be thereafter disclosed--as exposure to these cattle has health ramifications for all cattle, especially those intended for reproductive purposes. Marketing or movement of BVD PI animals in any manner that potentially exposes at-risk cattle is strongly opposed." Hoffman said transiently infected animals can also cause problems in a herd. "These animals may or may not show signs of sickness and will shed the virus for four to 15 days, but develop an immune response and eliminate the virus from their body," he said. "These cattle aren't as much of a problem as the PIs but they still can spread the virus for a short amount of time." PIs cause herd problems PIs are very efficient spreaders of the BVD virus because they shed it their entire life. A PI cow sheds virus to her calf and to other cattle on the farm, but a cow doesn't have to be positive to have a positive calf. "If you have one PI on your farm, it is costing you money," said Hoffman. Calves become PIs when their mothers are infected between 50 and 130 days of gestation. Once the calf is born, it can never become a PI. It must be born as a PI. According to Hoffman, cows have immune responses to BVD and won't become infected between 150 and 283 days of gestation. "A BVD negative cow can have a negative calf or a positive calf, depending on if she has been vaccinated or exposed at the critical time," he said. Only about 50 percent of PIs actually reach maturity; therefore, only 7 percent of PIs come from positive cows. Calves can be born from either a positive or negative cow, depending on how they are infected. Testing and vaccination are important Testing is the number one way to find problem animals in a herd, but vaccination against BVD is important, also. Testing can be done by taking an earnotch from each animal and sending it in to a lab for confirmation. A local veterinarian can assist with the procedure, which is very economical when producers consider the cost BVD can have on a herd, according to Hoffman. Vaccination of breeding animals should be done annually, to ensure protection for the fetus. The virus can also be shed through semen. Hoffman said, "Semen companies are very thorough at doing a multitude of tests to make sure they are not spreading disease, including looking for BVD. They also do processes that eliminate pathogens from the semen. "The big concern is not the AI sires; it is the seedstock supplier that is not checking his animals for the presence of a PI," he added. It isn't necessary to test the entire herd when looking for PIs, since a cow can be negative and have a positive calf. Hoffman suggests testing replacement heifers, bulls and new calves. If a PI is found, then the dam of that animal can be tested, as well, to determine if she is also a PI. "Nearly 75 percent of farms and ranches get BVD because they have purchased a heifer at the salebarn," said Hoffman. "Be smart and test the animals that are coming into your herd before they can cause problems." Jennifer Bremer can be reached by phone at 515-833-2120 or by e-mail at jbremermaj@hotmail.com. 2/4/08 Date: 1/30/08
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