Animal Profiling International

Greetings. It's Bruce Hoffman, DVM and president of Animal Profiling International. As I'm sure many of you know, it has been one of my biggest personal and professional goals to help educate people and increase awareness about the costly disease of Bovine Viral Diarrhea (BVD) and the persistently infected animals (PI) that are the major culprits of its spread. While much of the focus has been related to the beef market, it is vital to know that dairy animals run an equal risk of this disease.

Right now, with milk prices at all-time highs and many dairies expanding to help meet consumer demand, it is an excellent time to begin testing new heifers. With that in mind, we are fortunate to present Tom Shelton, MS, DVM of Intervet, Inc., to our readers in order to help provide more insight into these important issues.

Special thanks to Tom for his time and efforts in sharing his expertise with our readers of Herd Mentality.

Thank you Bruce. I'm Tom Shelton with Intervet. First of all, thanks to the audience for reading this newsletter. In my article I think it's important to stress that in our "Herd Mentalities" that it is very important we have a "BVD Mentality" as well.

Bovine viral diarrhea virus (BVDV or just BVD) has been with our dairy herds in the U.S. for a long time. It was first identified in 1946 and has been creating more questions than answers since then. A large range of clinical signs associated with BVD infection includes sub-clinical to severe acute disease. Noticeable signs include fever, inappetence, respiratory and gastrointestinal symptoms, infertility, increased embryonic mortality and fetal death, mummification and abortion. This obviously will have negative production effects reflected in young stock as increased morbidity (incidence of disease), increased mortality, reduced performance and higher culling rates. In adult cattle this is expressed as increased abortion rates, reduced conception and pregnancy rates and reduced milk production. Maybe as important as any of these overt signs are the immunosuppression caused by the virus that can increase a whole range of problems including mastitis, lameness and predisposition to opportunistic pathogens otherwise not expressed.

With the obvious negative consequences described, why haven't we been more concerned as an industry and can we eliminate this virus from our herds? Importantly, this virus can affect animals of all ages but also can infect fetuses' in-utero. If the virus infects a pregnant cow and is passed through the placenta to the calf somewhere in the vicinity of 40 to 120 days in gestation before the calf's immune system recognizes it as "foreign", it is allowed "carte blanche" privileges to infect and reproduce at high rates as long as that animal is alive. This is what is called a persistently infected (PI) animal that will shed huge amounts of virus to its herd mates and is responsible for the major part of new infections in animals in proximity to it. We are recently finding that the rate of these PI's are surprisingly high in some of our U.S. dairy operations (in the face of aggressive vaccination programs) and are maintaining the virus at sub-clinical levels within the herds that don't set off any obvious health alarms.

If all we have to do is identify and remove these PI's from our herds can we eliminate this disease? Yes and No. The virus can become "endemic" within a herd being passed from susceptible animal to the next and can also hide in "immunoprotected sites" like the testes. These, along with possible sylvatic (wildlife) hosts have the possibility to perpetuate the virus. Some Scandinavian countries where herd sizes tend to be smaller and much more isolated than our U.S. dairies have almost eradicated BVD by combining identification of positive animals for culling, biosecurity to reduce further exposure and surveillance to keep the virus out. Numerous health benefits have derived from these practices.

We have been vaccinating for BVD for years, why do we still have it in our dairy herds? BVD is an extremely complicated disease that in the face of all of the discoveries and advances of modern research may have secrets yet to reveal. While we have an environment conducive to frequent and widespread animal movement, large numbers in high density and minimal opportunities for isolation (all conducive to the virus) we do have some new tools available to help control/eradicate this problem.

Foremost is identifying those herds that harbor BVD PI's. If all newborn calves are tested (in addition to testing their dams of which a small percentage will be PI) and removed before exposure to the breeding herd the number of additional PI's will be reduced. With new and more specific testing protocols (able to identify positive animals) now available at reduced costs from running "pooled" or groups of samples together, we have both an accurate and affordable means to accomplish this.

Secondly, we need to set up a "biosecurity" protocol to reduce the chance of reintroducing BVD to the herd. This includes testing all adult additions, including bulls and purchased lactating animals as well as including samples from all calves born "dead or alive". Testing calves from Springer additions from outside of the dairy fits the same criteria for home grown heifers.

Thirdly, the use of modern modified live BVD vaccines (MLV's) that cover both genuses (type 1&2) that are USDA approved for the aid in prevention of PI's (the first trimester of pregnancy) or a newly approved claim for fetal infection (covering the entire pregnancy) are recommended pre-breeding on an annual basis. Although the vaccines are 90+% effective at controlling PI's it is a tall order to expect one vaccine to cover all of the possible strains and tissue preferences of the 1,000's of strains that are out there. Vaccination is an excellent adjunct approach for control, but testing and surveillance will be required to reduce this insidious problem.

Overstocking at the feed bunk increases aggressive behavior and prevents subordinate cows from accessing feed. "And who knows what kind of problems you're setting her up for," says Marina von Keyserlingk, of the University of British Columbia's Animal Welfare Program. Evaluate bunk management from the cow's perspective. "Cows don't normally stand like sardines in the pasture," von Keyserlingk said during a World Dairy Expo educational seminar. Rethink how much bunk space you offer cows. Is the industry standard of 24 inches acceptable? "We think it's probably not enough," von Keyserlingk says. Many experts now recommend 30 inches of bunk space per cow instead.

Animal Profiling International is proud to announce the addition of regional sales representatives that are much closer to you! Their knowledge of the industry in combination with the familiarity of the areas they service is vital in efforts to help assist and educate producers on a face-to-face basis in our battle against high-cost and deadly diseases within the cattle industry. Click the link below to find our expert nearest to you!

If you have any comments about the information in this newsletter, please either call us at 877.278.1344 or e-mail us at hq@animalprofiling.com. We want to hear from you!

© 2005. Herd Mentality is produced and distributed by Animal Profiling International, a technology company dedicated to animal health. You can subscribe to the newsletter at the Animal Profiling International Website.