TAKING a cue from what is known about improving human health through the use of soy and other bioactives, new research at the University of Illinois has found that increasing concentrations of soybean meal (SBM) above industry standards in the diets of weanling pigs may be beneficial for pigs infected with porcine reproductive and respiratory syndrome (PRRS) virus.
Ryan Dilger, a University of Illinois animal scientist who led the research, said the study was prompted by an observation reported from a large-scale commercial farm where pigs that were already on a higher-SBM diet did not become as sick during a PRRS infection.
Currently, PRRS is the most prevalent disease of swine globally. Young nursery pigs infected with the virus experience symptoms of fever, lethargy, respiratory stress, reduced feed intake and, ultimately, decreased growth performance.
Dilger said he wanted to find out if PRRS-infected pigs that were fed a diet containing a higher concentration of SBM would exhibit positive bodyweight gain during the time of infection as well as experience a shorter duration of illness. He found that, compared to PRRS-infected pigs that were not fed a higher-SBM diet, they did.
SBM is the primary dietary protein source for swine in the U.S. According to Dilger, soy-derived feedstuffs contain a number of biologically active compounds, including isoflavones, which may have been the key to reduced illness in the PRRS-infected pigs in the study.
"All this fits under the umbrella of looking for alternatives to antibiotics," Dilger said. "We are looking at alternative strategies we can use to keep promoting health during that time (of infection). Increasing soybean meal — something that is already used in swine formulations — is simple and effective and may be an important approach for the industry."
Typically, SBM is limited in the diets of newly weaned pigs because their still-developing gut is unable to digest the nutrients, which can result in symptoms such as diarrhea and reductions in food intake and growth. After weaning, the diet typically contains around 17% SBM, Dilger explained.
As part of his study, PRRS-infected weanling pigs were fed a common diet for one week, and then for the next two weeks, one group was put on a high-SBM diet of 29% SBM, while another group was put on a low-SBM diet of 17.5%.
During the two-week period of infection, blood tests showed less virus and fewer inflammatory markers circulating in the bloodstream of the pigs on the high-SBM diet compared to the pigs on the low-SBM diet. Fewer inflammatory markers may indicate an altered immune response, which appears to influence both the magnitude and duration of the illness for the infected pigs, Dilger explained.
"We still don't know exactly why this is happening. This was a proof-of-concept study, but we do know that the immune response is part of it," Dilger said. "Feeding a higher concentration of soybean meal elicited an improved immune response, and the next step is to identify whether this was caused by isoflavones or something else."
Dilger said the researchers speculate that the response is due to isoflavones but could not disentangle such evidence in this particular study.
Isoflavones are proven bioactives that are often emphasized in human nutrition and are known for having antiviral effects, Dilger explained.
"We know they are present in soybeans, so we quantified the amount, and we know that the diets with more soybean meal had higher isoflavones concentrations," he said.
Because SBM provides amino acids as well, Dilger said they are also looking into the effects of amino acids in the pigs' diets during PRRS infection.
Dilger pointed out that in healthy pigs, there is less benefit from consuming a higher-SBM diet, "but if you know your farm is at risk, then higher inclusion of SBM may serve as insurance. Soybean meal is expensive, so if you put it into the diet and it doesn't do anything, you've wasted money."
He added, "Nutrition won't prevent the infection, but it may lessen the negative effects."
China trade mission
A delegation of U.S. pork producers recently participated in an extensive trade mission to China.
"As the number-one consumer of pork and with nearly 20% of the world's population living in China, the Chinese market offers great opportunities for U.S. pork producers," Becca Nepple, vice president of international marketing for the pork checkoff, said.
The goal of the trade mission was to learn how to improve trade and build relationships among producers, importers and processing companies.
The delegation took part in the U.S.-China Swine Industry Symposium, a collaborative event co-sponsored by the U.S. Meat Export Federation and other agricultural organizations from both China and the U.S.
Held in Beijing, China, the symposium — "Is Bigger Better?" — focused on changes and challenges facing pork producers, processors and other members of the pork supply chain.
The symposium included the exchange of information on issues such as food safety, food security and sustainability.
National Pork Board chief executive officer Chris Hodges said, "We were able to meet with many top decision-makers, including company presidents and CEOs, and we picked up a lot of good information. We discussed trade opportunities and obstacles and the great potential for deep ties between the Chinese and the U.S."