Porcine Reproductive and Respiratory Syndrome (PRRS) continues to be a significant profit robber in U.S. swine herds, with an estimated annual cost of more than $600 million. The first part of a three-part webinar at PorkNetwork.com focuses on how producers can improve PRRS control in the breeding herd, in growing pigs, and in the entire system.

The three webinar segments can be watched separately or the complete webinar can be viewed in its entirety. The content is informative and useful to producers, veterinarians and allied pork industry representatives who have dealt with (or are dealing with) PRRS, and we encourage you to watch it.

Segment One: Live Virus or Modified-Live Vaccine?
The first segment features Montse Torremorell, DVM, PhD. She discusses breeding herd stabilization for PRRS, comparing live virus (LV) and modified-live vaccine (MLV) in a “load-close-expose” protocol. The findings are based on Dr. Daniel Linhares’ research study. Dr. Torremorell is an associate professor and is the Allen D. Leman Chair, Swine Health and Productivity in the College of Veterinary Medicine at the University of Minnesota (UM).

The study for which Dr. Linhares was the principal, involved 60 herds and took several years to complete. “One of the goals of the study was to put some science behind PRRS control and to determine what strategies were most effective,” says Dr. Torremorell.

Robert Morrison, DVM, PhD, professor in the UM College of Veterinary Medicine, was a moderator for the webinar program. He points out that the study was based on original work done by Dr. Torremorell, who found that by closing down a herd, the PRRS virus could be eliminated.

“What we built on top of that was to look at a whole sow farm exposure and how that might work, and whether we should use live virus or a modified live vaccine,” she says.

The researchers wanted to determine which of those strategies (using LV or MLV) would be more cost-effective for producers, and help them achieve PRRS-negative pigs faster in the nursery (called “time to negative pig,” or TTNP, which requires at least three months of negative tests).

Another important production metric is time to baseline production (TTBP). “This refers more to productivity and performance of the herd in a load-close-expose program,” explains Dr. Torremorell. “It measures how long it takes for the producer to recover from a PRRS outbreak and resume normal production.”

One of the primary objectives of the study was to determine how long it takes for a herd to produce negative pigs, and quite a range was evident. Dr. Morrison points out “The general rule of thumb had been 180 days, but the study showed it can be as short as 150 days, or as long as 300 days.”

This was one of the important outcomes, says Dr. Torremorell. “A great takeaway for producers is to allow plenty of time for the herd and the flow to be closed, and for the production manager to plan the breeding targets for the coming month.”

Immunity Matters
“We had information about the herds in the study, and they had had prior outbreaks of PRRS,” says Dr. Torremorell. “In this study, we found herds with prior immunity came to stability sooner.”

That immunity might have been from the actual virus or from the vaccine, but either way, herds that had been previously exposed to PRRSv returned to negative status more quickly than herds in which the animals had not been exposed to the virus.

Another take-home point from the study was that the live virus was much harder on the farm’s production compared to farms where the modified live virus vaccine was used. “We found the herds that used vaccine were able to reach baseline production sooner than those herds that had used live virus inoculation. That was one of the key differences between the two strategies,” says Dr. Torremorell.

Significant Difference
The difference was almost 1,500 pigs per 1,000 sows. If you do the math, with 3,000 and 5,000 sows, the number of pigs saved by using vaccine rather than the live virus was roughly double.

“When you look at the economic impact, including the cost of exposure, the cost of reaching stability, and the cost of a weaned pig, the numbers speak for themselves,” says Morrison.

The study is a major accomplishment, with significant and relevant findings for producers. Dr. Linhares study was funded through a Boehringer Ingelheim Vetmedica PRRS Research Award. Click here to watch the first segment of the webinar.