A three-pillar approach keeps BVD at bay

It was three years ago when John (the name has been changed) began to notice that more of his heifers were aborting calves. The issue raised questions, especially since he was concerned that he would not be able to produce enough replacement heifers for his growing 2,000-head milking herd. Then the test came back. Bovine viral diarrhea (BVD) had made its way into his operation.

"We'd always raised our own heifers, but we were in the midst of some expansion and had bought some calves," John says. "We suspect that a calf made it into our herd who was positive for BVD. We did not test like we should have."

A Devastating Disease

The herd was battling a disease that can significantly impact overall herd health and productivity. It often comes in without any overt symptoms, but the impact can be significant.

BVD can send shivers down any producer's spine. Conservative estimates put the cost anywhere from $35 to $65 per animal. Yet, that's not the worst part. BVD may be present in the herd, and you may not even know it.

"When the BVD virus infects a herd, we may not necessarily see clear-cut identifiable signs that we associate with BVD," says Linda Tikofsky, senior associate director of dairy professional services with Boehringer Ingelheim. "Its name is somewhat of a misnomer because diarrhea is not the most common symptom. The virus works on the animal's own immune system, suppressing it and making the animal susceptible to secondary diseases. A producer can also see reduced reproduction rates and more abortions."

The virus can move through the herd in a way you would think any disease would: through the interaction of an infected animal. It can also be present in persistently infected calves that show little or no outward symptoms but are viral machine factories; they shed the virus throughout the herd.

"If a pregnant female is exposed to the BVD virus, the growing fetus becomes infected through the dam. While most of these calves will die before birth, some will survive and not have any symptoms," Tikofsky says. "This is perhaps the most critical, because these calves are often grouped with other calves, spreading the disease."

How It Spreads

According to data from the National Health Monitoring System, the prevalence of the BVD virus recovered from bulk milk is 0% in small herds (identified as herds under 100 cows), 3.5% in medium herds (100 to 499 head), to more than 12% in herds greater than 500 head.

"The way we move dairy animals today does give the disease more opportunities to spread, but that doesn't mean it's a large-herd disease," Tikofsky says. "A large herd that tests for the virus and does not move animals may have a low risk, but the risk of contracting the virus to a 30-cow show herd that's moving around the country is higher."

Testing, Biosecurity, Vaccination

Short of putting your animals in a bubble, Tikofsky recommends a three-pronged approach – diligent testing, comprehensive biosecurity measures, and a good vaccination program – to ensure the virus stays out of your herd.

"Testing is paramount to identify animals that have the disease," she says. "Insist all animals that arrive on the farm are quarantined and tested before they enter the herd."

While testing can be tedious and there is a cost involved, the cost of BVD in the herd is significantly more. "With low milk prices, every management practice is scrutinized. If the last 300 tests have come up negative, you might question doing test 301 or 305," Tikofsky says. "But it just takes one animal to spread the virus through the entire herd."

Stringent biosecurity should be continually followed. "Producers need to ensure that when they move animals, they are not giving the virus a chance to move within the herd," she says. "Good biosecurity includes scrubbing boots."

A solid vaccination program can safeguard the herd against the virus. "There are several good products available to protect your animals," Tikofsky says. "Work with your veterinarian to set up effective vaccine protocols."

It's also imperative to ensure your herd is protected against all the types and subtypes of BVD. Another insidious feature of the virus is that it has mutated over time. In the 1970s, BVD Type 1 was the most prevalent. In the 1980s, it was Type 2. Within the two types are subtypes (Type 1A, 1B, and 2A). Currently, the most common subtype reported is Type 1B, which is not contained in any vaccine currently on the market, although a few have cross-protection.

"The virus is not stable, and while we have good vaccines, some do not show protection against the new subtypes. BVD may slip through even if you think you are protected," Tikofsky says.

Since discovering BVD in his herd, John has developed specific protocols. When first detected, every calf was tested. If positive, the heifer was tested. Positive tests meant an immediate cull from the herd. Now that the disease is under control, the farm continues to test calves regularly. The farm did have an issue with a calf testing positive, but it was quickly removed from the herd and no other cases have been identified.

For the past two years, the farm has not purchased any calves, maintaining a 100% closed system. All animals are vaccinated.

"We worked closely with our veterinarian to help us with protocols," John says. "It was not easy, but it just takes attention to detail and having a plan in place."

The bottom line: Maintaining a consistent, vigilant approach is paramount to keeping BVD out of your herd.

Editor's note: John, the Midwest producer who shared his story, is an anonymous name because of the stigma surrounding BVD. His dairy herd is highly productive and is a model operation.