New Monounsaturated Soybean Oil Works Well in Pig Diets

‘Improving the thickness of bellies, without compromising lean percentage’

By Lauren Quinn, College of Agricultural, Consumer and Environmental Sciences at the University of Illinois Urbana-Champaign

Adding a fat source to the traditional corn-soy swine diet is common practice, but the type of fat can make a difference both for growing pigs and carcass quality. Polyunsaturated fats, the primary type in dried distillers’ grains with solubles (DDGS), can reduce fat quality and complicate processing of pork bellies and bacon.

High-oleic soybeans, that are high in monounsaturated fats, create a stable oil valued by the food industry and nutritionists concerned with heart health. And according to new University of Illinois research supported by the United Soybean Board, high-oleic soybean oil performs well as a DDGS substitute both for growing pigs and pork processing characteristics.

The research team fed growing pigs a standard corn-soybean meal finishing diet, plus DDGS or high-oleic soybean oil (HOSO) as a fat source. They included DDGS at 25 per cent and the HOSO at two per cent, four per cent, or six per cent of the complete 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 Illinois and lead researcher on two new studies in the Journal of Animal Science.

soy bean crop
    Adobe Stock photo

In addition to growth performance, the first study 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. 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,” says Harsh.

The researchers found minimal differences in primal weights across the diets, but the overall trend showed greater fat thickness and reductions in fat-free lean as the HOSO percentage went up.

close up of pigs feeding
   Research showed an overall trend toward greater fat thickness and reductions in fat-free lean as HOSO percentage increased. -Jodie Aldred photo

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

A second study focused solely on loin and belly quality, including palatability, from the same set of pigs. Drilling down allowed the researchers 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 which 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. The loin is another primary outcome, so we needed to make sure we didn't have any major impacts on the loin either.”

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

Although the researchers evaluated three HOSO inclusion levels in the studies, they didn’t specifically intend to make a recommendation for the swine feed industry. However, based on their results, Harsh says the four per cent level looks promising.

“If we're talking about maximizing lean growth traits, the two per cent is probably best because those pigs are a little bit less fat. But the four per cent 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 six per cent level,” she says. “Looking at all the traits together, the four per cent HOSO inclusion seemed to be the sweet spot.”

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

“Diet cost per pound of pig weight gain was actually 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. But as high oleic soybean production increases, the price for HOSO will eventually go down.” BP

The studies, “Effects of feeding high oleic soybean oil to growing finishing pigs on growth performance and carcass characteristics” [DOI: 10.1093/jas/skac071] and “Effects of feeding high oleic soybean oil to growing-finishing pigs on loin and belly quality” [DOI: 10.1093/jas/skac284] are published in the Journal of Animal Science. Authors for both papers are Katelyn Gaffield, Dustin Boler, Ryan Dilger, Anna Dilger, and Bailey Harsh. Funding was provided by the United Soybean Board.

The Department of Animal Sciences is in the College of Agricultural, Consumer and Environmental Sciences at the University of Illinois Urbana-Champaign.

An Ontario Perspective - By Emily Croft

Discussions of high-oleic soybean production have recently become more popular. The production of niche crops can offer producers an opportunity to increase their returns while filling consumer demand for specialty products.

Until now, the major demand for high-oleic soybean production is with the goal of producing a soybean oil with a longer shelf life for the production of premade and packaged foods. Unsaturated fats are also considered healthier in terms of human nutrition, relative to saturated fats.

Based on this research from the University of Illinois Urbana-Champaign, these oils may also now have a place in animal nutrition, creating an outlet for high-oleic soybean oil products that may not qualify as food grade.

Dr. Martin Clunies, monogastric nutritionist with Grand Valley Fortifiers, says that while he has yet to see anyone growing high-oleic soybeans, he believes it may have a place in Ontario in the future.

“They could certainly be grown here; I don’t see any reason why not. We are in the same geography as Illinois and anything they could grow we could grow as well here in Ontario,” says Clunies, explaining that uptake of the new variety would likely be dependent on crop performance.

“If the yields are poorer than regular soybeans, it will have a difficult time being adopted. If yields are better, then I think it has a good chance of replacing regular soybeans.”

If crop performance is sufficient, the health aspects of high-oleic oils may contribute to a greater demand for monounsaturated, high-oleic soybeans as a fat source in pig diets.

“Oleic fatty acids have been shown to reduce the instance of coronary heart disease, so if you had soybeans that were high in oleic acid, that would make soy oil healthier. Then if you feed it to a pig and the pig incorporates that into fat depots or muscle, then you would think you would have a healthier fat depot in the carcass of those pigs,” explains Clunies.

Fats and oils may be included in grower pig diets to increase the energy density and improve feed efficiency. Clunies explained that this may be increased during the summer months. Producers can include fats to restore some growth when pigs are eating less due to heat. Current recommendations from OMAFRA suggest including no more than two per cent fat in grower and finisher diets.

It is also noted by OMAFRA that traditional oils may become rancid if not stabilized with antioxidants. This may risk the diet becoming unpalatable, leading to reduced feed intake. The increased shelf life of high-oleic soybeans can reduce this risk and avoid the cost of stabilizing additives.

Clunies says that while the increased shelf stability is a benefit, the new soybean may sacrifice some traditional soybean oil qualities.

“There is one downside. Soy oil isn’t typically thought of, but it has high Omega-3 fatty acids. But this will be decreased when you have high-oleic soy oil. You get something and you give up something,” says Clunies.

High-oleic soybean oil may be a feed ingredient and commodity that becomes more popular in the Canadian swine industry in the near future, due to both the stability of the fat and its health qualities. BP

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