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Study: High soymeal concentration in pig diets may help curb diseases

 

By DOUG SCHMITZ
Iowa Correspondent

URBANA, Ill. — A new University of Illinois study has found that increasing concentrations of soybean meal in the diets of weanling pigs, above industry standards, may be beneficial for pigs infected with the porcine reproductive and respiratory syndrome virus (PRRSV).
“Increasing soybean meal – something that is already used in swine formulations – is simple and effective and may be an important approach for the industry,” said Ryan Dilger, a University of Illinois assistant professor of animal science who led the research.
The study started when a large-scale commercial farm where pigs who were already on a higher soymeal diet reported their animals becoming less sick during a PRRSV infection. Currently, it is the most prevalent global swine disease, with young infected pigs showing symptoms of fever, lethargy, respiratory stress, reduced feed intake and ultimately decreased growth performance.
Dilger wanted to know if feeding PRRSV-infected pigs with a higher concentration of soymeal would display positive body weight gain during the time of infection, and a shorter duration of illness. According to his findings, pigs fed these higher concentrations did, compared to PRRSV-infected pigs that weren’t.
The study said soybean meal has been the primary dietary protein source for the U.S. pork industry, and Dilger said it contains a number of biologically-active compounds, including isoflavones that may have been the key to reduced illness in the PRRSV-infected pigs.
“All this fits under the umbrella of looking for alternatives to antibiotics,” he 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 maybe an important approach for the industry.”
According to a 2008 pork checkoff study, soymeal with hulls contained 44 percent protein, is a good amino acid balance in combination with corn and is palatable. The study, however, said it’s generally limited to 15-20 percent of the diet, or up to 25 pounds. It then can be used as the sole protein source after 25 pounds of weight.
Although soymeal is usually limited in the diets of newly-weaned pigs because of their developing guts’ inability to digest the nutrients – which can result in symptoms such as diarrhea and a reduction in food intake and growth – in weaned pigs, Dilger said the diet typically contains around 17 percent soymeal.
As part of the study, PRRSV-infected weanling pigs were fed a common diet for one week and then one group was put on a high soymeal diet of 29 percent, with another group put on a low soymeal diet of 17.5 percent for two weeks. 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 soymeal diet than in those on low soymeal.
He said fewer inflammatory markers may indicate an altered immune response, and subsequently influence both the magnitude and duration for the infected pigs. “We still don’t know exactly why this is happening,” Dilger said. “This was a proof of concept study, but we do know that the immune response is part of it.”
This may be the result of isoflavones, which he said are proven bioactives known for their antiviral effects. “We know they are present in soybean, so we quantified the amount, and we know that the diets with more soybean meal had higher isoflavones concentrations.
“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,” he explained. “We speculated it is the isoflavones, but we couldn’t disentangle that in this particular study.”
Dilger said his team is also looking into the effects of the amino acids in the pigs’ diets during infection. Conversely, in healthy pigs, there is less benefit of a higher soymeal diet, he said. “But if you know your farm is at risk, then higher inclusion of SBM may serve as insurance,” he said. “Soybean meal is expensive, so if you put it into the diet and it doesn’t do anything, you’ve wasted money.
“Nutrition won’t prevent the infection, but it may lessen the negative effects.”
Ron Birkenholz, communications direc-tor for the Iowa Pork Producers Assoc., said PRRSV has been a disruptive force in U.S. pork production for many years “and, as recently as 2012, was said to cost the industry more than $600 million each year.
“Obviously, more research will be needed to actually confirm the findings (of the University of Illinois study), but this is encouraging news,” he said. “PED (porcine epidemic diarrhea) has been the disease of greatest concern recently, but PRRS hasn’t gone away and continues to be an issue as well. If something can be found to lessen the severity of the illness in piglets, the pork industry will be much better off.”
12/3/2015