Monounsaturated soybean oil works well in pig diets

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Pigs were more efficient at converting diet into pounds of gain

PUBLISHED ON November 21, 2022

URBANA, IL — Adding a source of fat to a traditional corn-soybean ration for pigs is a common practice, but the type of fat can make a difference to both pig growth and carcass quality. Polyunsaturated fats, the main type in dried grains with solubles (DDGS), can degrade fat quality and make it difficult to process pork bellies and bacon.

High-oleic soybeans, high in monounsaturated fat, create a stable oil that is valued by the food industry and heart-healthy nutritionists. According to new research from the University of Illinois, supported by the United Soybean Board, high-oil soybean oil works well as a replacement for DDGS for both growing hogs and pork processing.

The research team fed growing pigs a standard corn-soybean meal, along with DDGS or high oil soybean oil (HOSO) as a fat source. They included DDGS at 25% and HOSO at 2%, 4%, or 6% of the total diet.

“When we fed high oil soybean oil, we saw a decrease in average daily feed intake, which makes some sense because when we put more energy in the diet, the pigs usually eat less. Pigs were more efficient at converting that diet into pounds of gain,” says Bailey Harsh, an assistant professor in the Illinois Department of Animal Sciences and lead researcher on two new studies in Journal of zootechnics.

In addition to growth performance, the first study focused on general carcass characteristics.

“When we think about what’s important to producers or to a standard commercial processor, it’s how these pigs are performing and yielding in terms of carcass weight and lean meat. We wanted to make sure it was all in one study so that the producer could look at it and say, ‘Well, this is how this affected my bottom line,'” says Harsh.

The researchers found minimal differences in baseline weight between diets, but the overall trend showed greater fat thickness and decreased lean lean mass as the percentage of HOSO increased.

“As we added more fat to the diet, going from 2% to 6%, the pigs grew more efficiently, but were a little fatter, and their carcass cuts went down a little bit, but not enough to make us too concerned,” Jorstka says.

The second study focused exclusively on loin and belly quality, including palatability, from the same group of pigs. The study allowed the researchers to assess whether diets affect the highest-value primary cuts.

“Bacon quality, like belly quality, is relatively dependent on the pig’s diet,” Harsh says. “When pigs eat a standard diet that contains DDGS and is higher in polyunsaturated fatty acids, those pig bellies will also be more unsaturated. We generally think of unsaturated fats as very soft or runny at room temperature, so you may have problems with the softness of the belly, making them difficult to cut. The lower back is another major outcome, so we needed to make sure we didn’t have major impacts on the lower back as well.”

Harsh says she saw very little effect on palatability, oxidation, or belly and loin quality in pigs fed HOSO compared to the DDGS diet. As expected, the bellies of pigs fed HOSO were fatter and firmer, with a higher proportion of monounsaturated fatty acids compared to pigs fed DDGS. And Korean chops were just as tender, juicy and flavorful in pigs fed HOSO as in pigs fed the standard industry supplement.

Although the researchers evaluated three levels of HOSO inclusion in the study, they did not set out to make recommendations for the pig feed industry. However, based on their results, Harsh says the 4% level looks promising.

“When we’re talking about maximizing lean growth traits, 2% is probably better because these pigs are a little less fat. But the 4% level is probably the best for increasing abdominal thickness and making it a little firmer without compromising lean percentage to the same degree as the 6% level, she says. “Looking at all the traits together, the inclusion of 4% HOSO seemed to be the sweet spot.”

Although HOSO achieves good growth and meat quality, Harsh producers note that they can still pay for this ingredient.

“The diet cost per pound of pig weight gain was actually slightly higher for the HOSO than the DDGS diet. However, we really think a lot of it is an affordability factor,” she says. “There is a lot of DDGS, so the cost is lower. Currently, HOSO is a small part of the total market, so it is more expensive. But as production of high-oleic soybeans increases, the price of HOSO will eventually fall.”

Studies “Effect of feeding pigs with high olein soybean oil fattening on growth and carcass characteristics” [DOI: 10.1093/jas/skac071] and “Effect of feeding high olein soybean oil to pigs on loin and belly quality.” [DOI: 10.1093/jas/skac284] are published in Art Journal of zootechnics. Both papers are written by Caitlin Gaffield, Dustin Boller, Ryan Dilger, Anna Dilger, and Bailey Harsh. Funding was provided by the United Soybean Board.

The department of zootechnics is located in College of Agriculture, Consumer and Environmental Sciences on University of Illinois at Urbana-Champaign.

— University of Illinois ACES