With new vaccines on the market, producers shold examine their herd health plans.

An effort to understand and control bovine virus diarrhea (BVD) in cattle herds has led to changes in vaccines and herd vaccine programs in the past few years. The addition of Type 2 BVD to most major vaccine lines was the first significant change. Following that came claims for fetal protection against persistent infection by two major companies (Pfizer with Cattlemaster and Bovi-Shield and BI with Elite and Express). Pfizer has recently offered additional claims in its new “gold” line of Cattlemaster and Bovi-Shield products which promise protection against abortion induced by infectious bovine rhinotracheitis (IBR). The gold line also promotes the safety of the modified live product (Bovi-Shield Gold) for use in pregnant cows and calves nursing pregnant cows when used according to label directions. This is where the biggest questions and concerns begin.

The questions include:

• Can I now use the modified live IBR/BVD vaccines on calves preweaning?

• Can I now use the modified live IBR/BVD vaccines anytime on cows, pregnant or not?

• If my mature cows had modified live vaccines used on them as cows, can I now just start using the modified live vaccines on them at any stage of pregnancy?

• Can I now give modified live vaccine to the cows at pregnancy check time?

The answer to each of these questions requires a look at the individual herd situation and the specifics of the vaccine label, especially the asterisks that lead on to fine print.

First, producers should know the BVD status of their herd before deciding on their herd vaccination plan. That will affect the results they can expect from implementing a plan. Herds currently containing BVD through active-infection or persistent-infection animals require different considerations than herds that have never been exposed to BVD vaccine before. The same goes for herds that have regular animal movement off-farm. It’s best to carefully examine these herd needs before jumping into use of the latest vaccine with the broadest claims.

Second, producers and veterinarians should read and understand the specifics on the vaccine label, including that asterisk that leads to the fine print. In the specific case of Pfizer products, the label states that “The Bovi-Shield GOLD line and PregGuard GOLD FP 10 may be administered to pregnant cattle provided they were vaccinated, according to label directions, with the Bovi-Shield FP line or the Bovi-Shield GOLD FP line prior to breeding initially and within 12 months thereafter. The Bovi-Shield GOLD line of products may also be administered to calves nursing pregnant cows provided their dams were vaccinated prior to breeding as described above.”

The label brings us to several points for consideration:

Cows that have never received this modified live vaccine should be vaccinated with it while they are open.

For best protection, that may also mean giving two doses, 2 to 4 weeks apart as we would with any new vaccine used on animals. I realize the two-dose suggestion is debatable, especially on cattle that have received annual doses of an IBR/BVD vaccine of another kind (killed virus and/or other brand) in years past. I won’t argue with existing protection. I’ll just suggest that the best protection with a new product would be obtained with a two-dose regimen.

Once cows have been vaccinated with this MLV product as open cows, they need an annual booster within 12 months after initial vaccination.

That comes under the 12-month duration of safety claim on the product. But it also means that if you vaccinate cows for the first time when they are open, and don’t provide next year’s booster until pregnancy check, you’ve gone beyond the 12-month recommendation. Is safety still there? Does protection persist between boosters?

Vaccinating calves with this modified live vaccine while they are nursing pregnant cows means that the cows they are nursing have to meet the same criteria mentioned earlier.

These points are only in regard to the newest “gold” lines of Pfizer products, not other vaccines from other companies.

Having made these four points related to the label, I’m still left with two other considerations related to use and timing of MLV vaccines for BVD in cows.

The first is that the best timing of BVD vaccine boosters for cows has been—and will always be—prior to breeding. That is because the window of opportunity for the BVD virus to infect pregnant cows and create persistent-infection calves is from day 40 to 125 of pregnancy. Therefore, it makes sense that boosting BVD immunity prior to that window is best for the cow, the calf and the herd. Waiting for the convenience of handling cows at pregnancy check time (often 60 to 90 days pregnant or at calf weaning) allows the previous year’s BVD vaccine immunity to have naturally declined and be of  indeterminate protectiveness for the early days of that important pregnancy window. I offer these concerns without any knowledge or study of what the actual duration of protective immunity is for MLV BVD use in cows. Remember, duration of immunity is not the same as duration of safety.

The second consideration is more of my own critical observation. I have no doubt about the testing data that led to claims for 12-month duration of safety and allowance for use in pregnant cows. But does anyone know what effect, if any, that the use of an MLV vaccine on a pregnant animal has on the life and performance of the fetus after it is born? I’m sure that would be a difficult and expensive question to answer. But I have that same concern no matter what the species or what the MLV vaccine might be.

To me, the bottom line regarding new and improved BVD vaccines is that these products are safe and effective and provide much better prevention and control of BVD than has been possible in the past. We simply need to be cautious and sure that we understand these products. We need to understand the situations in which they are being used. We need to use them according to a specific plan. And we need to have reasonable expectations for the results.

Dr. Tony Martin is a veterinarian and manager of animal health for MFA Incorporated.