Replace DDGS with monounsaturated soybean oil, studies show

A balanced pig diet contains two main components — energy and amino acids. While adding a fat source to a traditional corn-soybean-meal diet is common, the type of fat can impact both growth and carcass quality. Distillers’ dried grains with solubles (DDGS) have been used in pig feed for several years. However, DDGS contain high levels of polyunsaturated fats, which can reduce fat quality and complicate the processing of pork bellies and bacon.

DDGS substitute

High oleic soybean oil works well as a DDGS substitute for both growing pigs and pork processing characteristics, according to research by the University of Illinois. High in monounsaturated fats, the oil became available about a decade ago as the food industry phased out its use of partially hydrogenated oils.

In the University of Illinois study, researchers fed growing pigs a standard corn-soybean-meal finishing diet as well as DDGS or high oleic soybean oil (HOSO) as a source of fat. DDGS was included at 25% and HOSO at 2%, 4%, and 6% of the pigs’ entire diet.

“When we fed the high oleic soybean oil, we saw reduced average daily feed intake, which makes some sense because as we include more energy in diets, pigs will usually consume less. The pigs were more efficient in converting that diet into pounds of gain,” says Bailey Harsh, assistant professor in the Department of Animal Sciences at the University of Illinois.

Besides growth performance, the study also focused on overall carcass characteristics. “When we think about what is important to producers or to the standard commercial finisher, it’s how those pigs perform and yield in terms of carcass weight and fat-free lean,” Harsh says. “We wanted to make sure all of that was in one study so a producer could look at that and say, ‘Well, here’s the impact on my bottom line.’”

The research revealed minimal differences in primal weights across the diets. Overall, it showed greater fat thickness and reductions in fat-free lean as the percentage of HOSO increased.

“As more fat was added to the diet, moving from 2% to 6%, the pigs grew more efficiently, were a little bit fatter, and their carcass cutability dropped a little, but not enough that we would be too concerned,” Harsh says.

Second study

The same pigs were also part of a second study, titled “Effects of Feeding High Oleic Soybean Oil to Growing-Finishing Pigs on Loin and Belly Quality,” led by Harsh. By focusing on these two areas, researchers were able to evaluate whether the diets affected the highest-value primal cuts.

“Bacon quality, as well as belly quality, is relatively dependent on a pig’s diet,” Harsh says. “If pigs are consuming a standard DDGS-containing diet that has more polyunsaturated fatty acids, those pork bellies will also be more unsaturated.

“We usually think about unsaturated fats as being very soft or liquid at room temperature, so you can have problems with softness of the bellies that can make them hard to slice,” she continues. “The loin is another primary outcome, so we needed to make sure we didn’t have any major impacts on the loin either.”

In addition, Harsh says there was minimal effect on palatability, oxidate, or belly and loin quality in pigs fed HOSO compared with the DDGS diet. Researchers also noted that the bellies of the HOSO-fed pigs were thicker and firmer, with a higher proportion of monounsaturated fatty acids compared with DDGS-fed pigs. The loin chops were just as tender, juicy, and flavorful in the HOSO-fed pigs as the animals fed the standard supplement.

Sweet spot is 4%

Even though three HOSO levels were evaluated in the studies, researchers hadn’t planned on making recommendations for swine feed. However, results show 4% looks to be the most promising level.

“If we’re talking about maximizing lean growth traits, 2% is probably best because those pigs are a little bit less fat. But the 4% level probably is best for improving the thickness of bellies and making them a bit firmer, without compromising lean percentage to the same degree as the 6% level,” Harsh says. “Looking at all the traits together, the 4% HOSO inclusion seemed to be the sweet spot.”

While HOSO achieves good growth and meat quality characteristics, Harsh notes producers may pay a premium for the ingredient.

“Diet cost per pound of pig weight gain was a little more for HOSO than the DDGS diet. However, we really think most of that is a factor of availability,” she says. “DDGS are plentiful, so cost is lower. HOSO currently makes up a small portion of the total market, so it is more expensive. As high oleic soybean production increases, the price for HOSO will eventually go down.”

Both studies were published in the Journal of Animal Science and funded by the United Soybean Board.