What’s the effect of adding back soybean byproducts into soybean meal when feeding pigs?
K-State assistant research professor in swine nutrition Katelyn Gaffield and her team are studying this novel factor because soybean meal has served as one of the largest protein sources in swine diets over the years.
“I studied this during my doctoral research with the team, and these are – specifically – the byproducts from oil refineries; we can get soybean gums or soybean soapstocks,” Gaffield says. “We conducted a large industry survey, and with the help of the United Soybean Board, we sampled from 15 different processing plants to look at the variation.”
Several interesting findings surfaced from the survey, including the large variation in color and viscosity.
“When we evaluated those samples of gums and soapstocks, we found large differences in the fat content, which was important when adding it back to diets and the moisture content,” she says.
Gaffield observed an increase in fat in the soybean meal when those byproducts got added back, but she did not observe a change in crude protein levels.
“Essentially, those plants add those byproducts back until they either hit their limit or until they’re worried about getting too low of a crude protein content in the soybean meal,” she explains.
Good News for Producers
Gaffield then conducted a nursery study where soybean gums and soapstocks were incorporated back into soybean meal to see if the increase in fat content and additional energy could be a benefit to pigs.
“Ultimately, we found little differences in growth performance when we fed the soybean gums or soapstocks to pigs,” she says. “So, this is a good finding for producers because it indicates that you don’t have to worry about sourcing different soybean meals and whether byproducts must be included back.”
Her team also uncovered a slight positive increase in average daily gain due to higher levels of gums, especially in the late nursey period. The researchers believe this is because gums have a higher level of fat content in the byproduct itself.
“Maybe we are seeing a potential benefit to the energy and no concerns with sourcing it for your swine diet,” Gaffield says. “There may be a potential benefit if you add it at high enough inclusion levels, but we need to evaluate that further to say it has a definite improvement.”
In addition to average daily gain, Gaffield’s team monitored fecal output.
“We also saw no differences in the fecal dry matter, which indicated it wasn’t negatively impacting their health or giving them gastrointestinal tract challenges,” she points out.
Gaffield reminds producers, however, that these byproducts were added back at relatively low levels.
“We only added up to around 2% and so even though we saw those large variations in energy content; it’s diluted out of the diet, so we didn’t see any negative effects there,” she adds.
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