OSHAB PRRS Survival Series - Update 4: Some victories in the battle, but some challenges and worries remain
Monday, December 10, 2007
In recent issues, we have followed the stories of several Ontario producers as they grappled with PRRS during the tough market conditions of 2007. This update reveals some surprises as well as challenges with monitoring the actual PRRS status in barns
by KATE PROCTER
The Vanden Boogaards of Gorrie, Huron County
Recap: Piet Vanden Boogaard's 900-head sow herd broke with PRRS in November 2004. The Vanden Boogaard herd was affected mostly in the nursery and finishing facility, where it suffered from higher mortality rates, slower growth rates and higher cost of production. The Vanden Boogards' aim is to start producing PRRS-negative piglets in order to produce PRRS negative replacement gilts.
At our last visit, the Vanden Boogaards were "going steady," said Piet. They had started following a rigorous protocol when introducing new gilts into the herd. The gilts were vaccinated with PRRS serum, isolated and then blood-tested to ensure that they were PRRS-negative before introduction into the sow herd.
In spite of this, they were having a nagging scour problem in the newborn piglets. They tested for all the usual culprits, including E. coli and salmonella, but came up with nothing. After having ruled everything else out, they started digging more deeply and discovered that the vaccine strain of the virus that they had used in the herd in 2005 had mutated and that they were now fighting two different strains of PRRS.
"The persistence of the scour problem led us to believe there was something else going on here," says herd veterinarian Dr. Greg Wideman. He explains that they had been successful in reducing the prevalence of the field strain of PRRS to the point that the mutated vaccine strain had become dominant and was now causing problems. While the gilts had been successfully vaccinated against the field strain, this was doing nothing for the mutated strain. As these gilts moved into the main barn, they were causing a flare-up and a noticeable increase in scour problems.
This situation has reinforced Wideman's theory that tackling the virus as early as possible is vital to maintaining control. "When you've got a PRRS problem, you've got to deal with it right away because it just gets more complex," he concludes.
Action: The Vanden Boogaards serum-vaccinated the entire sow herd with the field strain of PRRS mid-October. Three weeks later, they vaccinated the entire sow herd again, but this time with the mutated vaccine strain of the virus. While there is no generally accepted protocol for tackling two strains at the same time, Wideman says that they did not want to mix the viruses in order to vaccinate in one shot, but at the same time they did not want to drag it on longer than necessary. He explains that interpreting lab results in the presence of two viral strains would be too complex, so it is important to eliminate both.
Four to six months following inoculation, they plan to begin testing piglets at weaning before they go into the nursery. The nursery is completely contaminated with PRRS, explains Wideman, and they hope to clean it out but will not start on that until the summer of 2008.
Darryl and Cheryl Terpstra, Birchlawn Farms, near Dorking
Recap: The brother and sister team of Darryl and Cheryl Terpstra have a 900-head sow herd with an on-site nursery and have battled various disease issues over the years, breaking with PRRS again in December 2006.
At our last update, Birchlawn Farms was seeing good results from the nursery, with a decreasing number of PRRS-positive results coming back from routine blood tests. Unfortunately, the next test came back with all pigs testing positive for PRRS virus. Darryl Terpstra says there could be several explanations for this outcome. Because of current market conditions, two of his feeder pig buyers backed out of their contracts with him. As a result, Terpstra was forced to hold his pigs longer than normal, which meant that his nursery contained pigs of a much wider age range. He suspects this helped circulate the virus through the pigs left in the barn.
For now, Terpstra is sending his pigs to finish in Iowa, retaining ownership of 75 per cent of the production from his sow herd. "I don't know if this is going to help us or kill us, but it moves the problem away," he says.
Terpstra stresses that in spite of the positive PRRS test results, his pigs are performing well and look good. He has had no complaints from buyers and had a 1.5 per cent mortality rate on the nursery group that tested positive for PRRS virus. In that same group, only 1.5 per cent did not make the top grade and he was confident before the test results came back that they would all be negative.
Dr. Martin Misener, the herd veterinarian, explains that this herd looks good from a clinical standpoint and that, given their previous negative blood test results, the "industry would typically call this herd stable."
In fact, says Misener, the herd is not stable. He illustrates the difficulty this way. It is like reaching into a big jar filled mostly with blue jellybeans but with a few red ones spread throughout. How many times do you reach into the jar and get a handful that contains no red beans?
Action: The Terpstras will continue to monitor the pigs, using blood tests in order to study the trend and see if it matches the clinical results in the barn. They will discuss making a breeding break, but would not consider taking this action until March. Misener explains that this is the optimal time to make a breeding break because the pigs that are born as a result of March breedings would be marketed in December, a time when markets are traditionally at their lowest value. "We try to minimize exposure on money-losing markets," explains Misener.
Ron and Glen Manjin, Teeswater Pork, Huron County
Recap: Ron and Glen Manjin manage Teeswater Pork. They were in the process of filling their 2,300-head sow unit when they received PRRS-positive gilts in the final load in November 2006. They have brought in no new gilts since December 2006.
"Everything at Teeswater Pork is going extraordinarily well," says Dr. Martin Misener, their herd veterinarian. Because the gilt supply was interrupted and they are managing a start-up herd, the Manjins realized that they were going to have a period where they would have less than one third of their weekly breeding target to breed. Rather than do this, they decided to stop breeding altogether and had a three-week breeding break in May. They took advantage of the resulting farrowing break to remove all the piglets from the barn.
Misener explains that, before the break, the Teeswater herd was experiencing a low-level of PRRS virus prevalence. Since the break, the sows have been consistently weaning PRRS-negative piglets. "I think we could do this in every herd, every time," says Misener.
At present, the piglets are still testing negative and 21 sentinel gilts that have moved into the herd have also tested negative after four weeks in the sow barn. Misener says that he would now classify this herd as "stable."
Action: The Manjins will continue to test piglets coming out of the nursery on a sporadic basis, monitor the sow herd with quarterly testing and bring only negative gilts into the herd. Their goal of eradicating PRRS from this herd will be reached when the last seropositive sow is shipped, Misener explains.
They plan to buy between 200 and 300 gilts of different ages at a time in order to fill their gilt isolation barn, and then close the barn for one month before blood-testing all the animals. If they test negative, they will start biofeedback to expose the gilts to their sow barn environment before moving them into the main barn. Biofeeding may consist of collecting, freezing and grinding mummified piglets, weak newborns and stillborns. This is then mixed with manure from newly farrowed sows and sows with scouring litters and floor fed to sows and gilts before farrowing.
Gerald and Donna Jantzi, Gerdon Farms Inc., near Millbank
Recap: The Jantzis have two 1,450-sow units, Burnside and Gerdon, with weaned piglets co-mingled in four separate nurseries. Pigs then go to one of 10 separate finishing facilities. The Burnside sow unit broke with PRRS in late November of 2005 and then relapsed in mid-March of 2007. The Gerdon Unit also broke with PRRS in mid-February 2007, but with a different strain than that affecting the Burnside unit.
Gerald's new Gilt Development Unit is working well. He placed two groups of gilts there over the summer and started breeding them in mid-October. They had some initial positive test results on nursery pigs sampled late summer, which were followed by negative results.
Action: They continued doing PCR tests for PRRS throughout October and November. Sentinel pigs started going into the barns in mid-October and they started giving biofeed back to open gilts at that time.
Martin and Teresa Van Raay, Dashwood, Huron County
Recap: The Van Raays operate a 500-head, farrow-to-finish herd that is continuous flow and they generate their own gilts. They had a PRRS outbreak in March 2006. They have not entirely given up on removing PRRS from the herd, but for now Martin says "we're going to let things stay as they are."
Update: The Van Raay herd has nothing new to report and is continuing to produce pigs with no plans for PRRS eradication in the near future.
Bill MacDougald, MacDougald Pork, near Fullarton
Recap: Bill MacDougald operates a 1,350-head sow herd and sells the feeder pigs produced by those sows. The herd experienced a PRRS outbreak in November, 2006.
Update: MacDougald's operation has been successful in eliminating PRRS from the barn. "We walked PRRS out of the barn in textbook fashion," says MacDougald. The eradication procedure was a success with both the sow herd and the nursery testing negative for PRRS.
From April to September, MacDougald says his sows were weaning 24.3 pigs per sow per year, with each month seeing a slight increase. September's records showed 25.3 pigs per sow per year and 600 pigs per week were weaned for the first three weeks in October. MacDougald explains that some of the management improvements they made prior to the PRRS outbreak have finally had a chance to work now that the virus is again out of the herd.
In spite of the successful eradication procedure, MacDougald still feels the shadow of the disease hanging over his head and he worries that it might come back into the barn. This, coupled with exceedingly tough market conditions, has him considering his future in the pork industry. "I think this is going to be a pivotal crisis," he says. BP