For most human moms, pregnancy means morning sickness, weight gain and irrational cravings for pickles. But with pregnant pigs, the real pickle is that diseases like PRRSV (Porcine Reproductive & Respiratory Syndrome Virus) can be passed to the fetus, sometimes with fatal results. Addressing that problem is a key focus of a new Genome Alberta research project, which seeks to apply genomics to improve disease resilience and reduce pig deaths and morbidity.
The project comprises four main activities, and one in particular -“Activity 1.4 - Pregnant Gilt Model 2 (PGM2)” – tackles the issue of reproductive PRRSV.
“This is the second Pregnant Gilt Model,” said Project Lead Dr. John Harding from the University of Saskatchewan. “The first one gave us a much better understanding of phenotypic responses to PRRSV in pregnant pigs, immune responses in dams and why some fetuses are dying.”
As Jaws II demonstrated, not all sequels are noteworthy. According to Dr. Harding, however, PGM2 will give industry a lot to chew on.
Focus on the fetus
“We want to look at how PRRSV crosses the placenta, as this is not fully understood,” said Harding. “Then we must determine what is happening to the fetus.”
The first Pregnant Gilt Model found that once the virus enters the placenta, it probably passes from fetus to fetus. Yet some fetuses and even entire litters prove resistant, and understanding why could go a long way to preventing that passage.
“In some cases, gilts can be fully infected and still produce a completely negative litter, which is quite remarkable.”
Apart from restoring our faith in sequels, the PGM2 could have far-reaching benefits for producers.
“Ultimately, we’re looking for bio markers that are indicative of fetal resistance to PRRSV infection,” said Harding. “This could allow us to select for increased resilience and might even represent an alternative to PRRSV vaccination, which has its own challenges.”
In the event of a PRRSV outbreak, the animals with greater resilience may perform better, so that the disease would be controlled faster and breeding systems could be developed to produce more resistant pigs.
As excited as he is about what they’re doing, Harding is equally enthused about how they’re doing it.
“There have been a lot of research papers on this and studies done in test tubes, but very few experiments that focused on live, pregnant animals.”
Also, because reproductive studies of live animals are expensive and labor intensive, those that have been done used only a handful of subjects. By comparison, PGM2 involves 60 gilts, making it a leading edge project.
“Nobody has that kind of data. People worldwide are realizing that this is a huge project with a very clean data set, so it’s really showcasing Canada, which is excellent.”
Cutting our losses
With all the diseases today, why focus on PRRSV? It turns out there are over half a million reasons to do so.
“The economic losses associated with PRRSV are staggering. In the United States alone, they amount to $664 million a year, with about half of that attributed to reproductive PRRSV.”
Having said that, Harding foresees a research movement away from individual diseases and into general, global disease resistance to reflect the growing number of afflictions in the pork industry.
“These diseases impact not only production and economics, but also welfare and public perception. The more fetuses we can save, the better our reputation with consumers.”
Unlike Jaws II, this is one sequel you can really sink your teeth into.