Art and Ken Lehmann started a commercial sow herd at Strawn, IL, in 1969, their first leap into confinement hog production. The basis for that original herd survived for three decades. But they knew their operation was living on borrowed time.
Amazingly, in all those 30 years, the Lehmanns never depopulated the whole breeding herd nor completely cleaned out the farm of hogs.
It took a severe outbreak of PRRS (porcine reproductive and respiratory syndrome), a disease they struggled with since 1993, to write the herd's final chapter in 1999. Depopulation was completed in May on the main herd at Lehmann Farms.
After repopulation, the breed-to-wean operation now stands at 1,400 sows. Nursery and finisher units are all contracted.
Even though the old herd didn't survive PRRS, some of the vaccine and management steps, which had a valuable impact on reproduction and growth, did. Those steps are being carried forward and used in the repopulated herd and others the Lehmanns own and/or manage today. Art runs the hog operation, his brother Ken the grain operation.
Health Hits Snag During those years managing the original breeding herd, Art purchased herd replacements through multiple genetic sources. He dealt with a variety of disease organisms. But overall, herd health was good.
That all changed in 1993. PRRS struck and herd health quickly deteriorated. "We had a very unstable situation in our sow herd," Art recalls. "We had both reproductive and respiratory forms of the disease - early farrowings, abortions and a variety of respiratory problems in finishing."
The list of herd health problems precipitated or made worse by PRRS read like a "who's who" of swine diseases: E. coli diarrhea, atrophic rhinitis, salmonella and porcine respiratory disease complex (PRDC) problems including swine influenza virus, Haemophilus parasuis and Mycoplasmal pneumonia. As a result, there were big problems getting sows to farrow a litter of healthy pigs and slow-gaining pigs through finishing.
Vaccine Action When the first modified live virus (MLV) PRRS vaccine (from BI/NOBL Laboratories) was introduced in 1994, Lehmann immediately gave it a try. All sows were vaccinated twice, two weeks apart, then went on a quarterly vaccination program.
Safety concerns led some veterinarians to advise producers not to vaccinate first-trimester sows for PRRS.
Art switched to a new approach called the "6-60" program. It calls for vaccinating sows six days after farrowing and 60 days after breeding.
Even though Art had vaccinated for PRRS for a year or so, it seemed the disease still managed to make all the pathogens in the herd worse.
On the advice of a veterinarian, Art tried lowering pig weaning age to get rid of persistent problems with rhinitis, mycoplasma and Streptococcus suis. He tried weaning at 14, 12 and 10 days of age. None worked. It proved hard to get sows to return to estrous and to get young pigs weaned and converted to solid food. Art returned to a weaning average of 16 days of age. He also tried vaccinating for awhile in 1995 with a second PRRS MLV vaccine from Schering-Plough Animal Health.
The long-time Illinois producer observes: "We kind of struggled along. We were really frustrated after fighting this disease for five years."
New Vaccine Introduced Art's veterinarian bled sows periodically since starting the MLV vaccination program for PRRS. Results bore out what he suspected was happening. The vaccine was not evenly protecting his breeding herd. Some sows had extremely high PRRS antibody titers. Some had mid-range levels and other sows registered no titer at all.
Antibody titer is a measure of how much antibody is circulating in the pig's bloodstream. Titers are supposed to increase, at least temporarily, after a pig is exposed to natural infection or vaccination.
It didn't matter how sows were tested - whether randomly or right down a row. Subpopulations (wide ranges in titer levels) were always there, asserts Art.
"We had these severe problems with subpopulations despite the fact that some of these sows had 8-10 vaccinations," he says.
Art was at an impasse as to what to do next. Then he started to work with veterinarian Karen Lehe, Wolcott Veterinary Clinic, Wolcott, IN.
In early 1998, the first and only federally approved killed virus vaccine for PRRS was introduced (PRRomiSe from Bayer Animal Health). Veterinarians had been making killed, autogenous vaccines for PRRS for several years. But there was doubt in industry whether a commercial, killed PRRS vaccine could be protective, he points out.
Still, Lehe and Art Lehmann agreed the killed virus vaccine was the producer's last hope.
Together they designed a protocol to "test" the potential of the killed virus vaccine. First, they blood tested a group of 62 crated sows in a row with a common water trough. The group was previously vaccinated with an MLV vaccine and all bred in one week.
The ELISA test serology results of those sows gave them a baseline of blood levels for PRRS (Table 1). Surprisingly, average titer was only 0.48. The cutoff for a "positive" titer indicative of antibody development is 0.4, says Lehe. Those sows were then vaccinated with the killed virus vaccine. Two weeks later, the sows were blood tested again.
Two weeks later, the group was split. Half received a second dose of killed virus vaccine, half did not. "So really what we were looking at was what one dose of killed vaccine did to the titers vs. two doses," explains Lehe. "We wanted to see what kind of immune response the vaccine was going to give us." She points out that even if titer levels rise, it doesn't mean that the sows are protected from PRRS.
The average titer of blood-tested sows two weeks after being given the first 2 cc. dose of PRRS vaccine went from 0.48 to 1.0, a nice increase in response to the injection, she says.
The average titer of the 30 sows that received a second dose of the killed vaccine went from 0.93 to 1.4. The average titer of the sows that did not receive a second injection stayed at about 1.0, says Lehe.
The Indiana veterinarian emphasizes the work at the Lehmann farm was not a controlled study. There was no control group and no statistical analysis was performed. The only purpose of the protocol was to measure production parameters before and after the killed virus PRRS vaccine was administered.
From the results of the protocol, Lehe determined that one dose of the killed virus vaccine was nearly as effective as two.
Vaccine Rotation Art Lehmann declares: "As soon as we got those results back in late January 1998, we went ahead and vaccinated our entire sow herd 60 days postbreeding with the Bayer killed virus vaccine, combined with the use of Schering's MLV vaccine six days after farrowing.
"And we continued to use that PRRS vaccine rotation," he notes.
Some reproductive performance areas improved in just two months after vaccine rotation started. Overall, litters were larger by almost one pig, farrowing rates improved a few percentage points and non-productive sow days were reduced by 12 days (Table 2).
Art also beams when he talks about the change in nursery performance. He says based on 40 nursery closeouts, before and after the vaccine rotation was used, feeder pigs are going out the door to contract finishers weighing an average of 62.5 lb. Before the vaccine rotation, weights averaged 55.2 lb.
"We saw a tremendous difference in the average daily gains of the pigs when we started weaning after the sows had been injected with PRRomiSe vaccine," observes Art.
By September '98, he thought he finally had a sow herd he could live with. But opportunity and reality changed his mind.
The opportunity was a chance to buy a large group of feeder pig replacement gilts at fire sale prices because a breeding stock multiplier was going out of business.
The reality was that, despite greatly improved sow and pig performance, PRRS vaccines couldn't overcome all the health problems of a 30-year-old herd.
"Even if we managed to cure all the things on the sow side, we were locked into a pretty heavy vaccination program on our pigs," he continues. Sows were being vaccinated for rhinitis, SIV, PRRS, strep, Haemophilus parasuis and parvo/lepto. Pigs were being vaccinated for rhinitis, mycoplasma and PRRS.
Since repopulating, rhinitis injections have been eliminated in sows and pigs, and PRRS vaccination has been eliminated in pigs, saving the operation $1.40/pig in vaccination costs, he says.
New PRRS Program In the new herd, Schering's MLV PRRS vaccine is only given to replacement females at 100 lb. Sows are on the "6-60" program but only the killed virus vaccine is being used. As a result, Lehmanns are now weaning pigs that test negative for PRRS.
Boars are now housed offsite in a boar stud. Only killed virus PRRS vaccine is given to boars, one dose on arrival and a quarterly booster.
Only 75 grandparent gilts are added to the herd in a year's time. They are purchased as 14-day-old pigs and are raised in an offsite, isolation nursery and finisher. When they reach 220 lb., they are brought to the sow farm, isolated 30 days and acclimated 30 days before entering the sow herd. Parent gilts are raised from these grandparents.
Art readily admits that his experiences with PRRS and the vaccination program may not be for every herd. "PRRS presents itself differently on every farm," he explains. "On some farms, producers hardly know it's there. On others, especially where there are a number of other disease organisms present, it just wrecks them."
At BLT Pork, a multiplier operation he and Ken are part owners of and provide management for, production runs 23-24 pigs/sow/year and has for three years. BLT uses the "6-60" program with just BI/NOBL's MLV PRRS vaccine. Herd and buildings are only seven years old and the disease load is fairly low.
In contrast, RB Swine, another herd Art manages, has successfully used the "6-60" PRRS MLV (BI/NOBL) and killed vaccine rotation he first used, for almost two years.
He stresses the killed vaccine has proven to be both safe and effective when used in sows and boars. "I do believe it builds immunity. I think when an animal has already been exposed either to the field virus or the MLV vaccine virus, I think the killed virus vaccine enhances protection," he observes.
Art stresses: "If your PRRS vaccine program is working, don't switch. But if the results leave something to be desired, consider trying another approach. Base the results of that vaccine on the performance you think you should be getting."