Mannan oligosaccharides (MOS) can be fed to pigs to boost immunity, according to a new University of Illinois study.

“When it comes to keeping pigs healthy, there are some potentially powerful tools we can use in the diet besides antibiotics,” says James Pettigrew, University of Illinois professor of animal science. “We have a tendency to think that we can administer health through a needle, by giving pigs antibiotics, and even through systems like all-in, all-out pig flow. These are important, but there are also many health benefits we can realize through the diet.”

MOS is a product made from the cell wall of yeast containing carbohydrates that may provide special benefits, Pettigrew says. Previous research showed that it increased the growth rate in newly weaned pigs and changed the microbial populations in the digestive tract.

Pettigrew’s postdoctoral research associate Tung Che led two studies looking at MOS and its effect on pigs experimentally infected with porcine reproductive and respiratory syndrome (PRRS) virus. Researchers evaluated how feeding MOS can modulate immune responses in pigs infected with PRRS.

“We found MOS can enhance immune responses in pigs, but it can also alleviate the overstimulation of the immune system,” Che says. “MOS increases the total number of immune cells such as leukocytes and lymphocytes in the blood at the early stage of infection.”

The findings could be beneficial to producers fighting PRRS, a respiratory disease that causes a reduction of immune cells.

“This is important because the increase in leukocytes and lymphocytes can help the animal to fight not only PRRS, but also secondary bacterial co-infections that are common with PRRS,” Che says.

Seven days after this PRRS inoculation, fevers were reduced in pigs and feed efficiency was improved, suggesting a reduction of ongoing inflammation.

“We wanted to find out why MOS enhances the immune system, but at the same time alleviates the overstimulation of the immune system as observed by reduced fever,” Che says. “So we collected white blood cells and measured gene expression by using a broad microarray technique followed by the more specific quantitative polymerase chain reaction.

Again, the results reflected enhanced immune response and the reduction of fever, Che says.

“MOS stimulates the immune system and enhances the immune response, except when the immune system is already challenged,” Pettigrew explains. “MOS actually reduces the inflammatory response in pigs with challenged immune systems. This may be how the product improves growth performance because it redirects nutrients to growth rather than the immune system.”

Che says MOS also improves feed efficiency from Day 7 to 14 after inoculation with PRRS.

“PRRS interferes with the immune response and makes pigs more susceptible to bacterial infections,” Pettigrew says. “This product seems to counteract this effect. It may even reduce bacterial infections associated with PRRS, although we did not test that specifically.”

The research team is repeating this experiment with a second generation of MOS-like products to learn more about how this mechanism in MOS works.

“We are increasingly concerned about the importance of keeping pigs healthy, so we direct much of our research program to looking at things we can do in the diet to improve the health of pigs,” Pettigrew says.

The research team also included Bill Van Alstine of the Animal Disease and Diagnostic Laboratory at Purdue University and Karl Dawson and Colm Moran of Alltech, which provided funding for the study.