By Anna Dilger, University of Illinois
We often hear “You are what you eat.” Did you know that this is often true for pigs as well? What pigs eat can alter the composition of their meat—and not just how much fat or protein they deposit. Certain fats or fat-soluble compounds eaten by pigs can be deposited in pork fat and cause meat to have unusual flavors, off-odors, or poor shelf-life. This phenomenon made producers and processors concerned about a particular component in swine diets—oxidized oils—and how feeding oxidized oils may be affecting pork quality.
Why do fats and oils matter?
Fats and oils are an important component of diets for pigs. They provide energy and essential fatty acids that pigs need to grow. Some common sources of fats and oils in swine diets can be corn oil, choice white grease, or byproducts like animal and vegetable fat blends and used restaurant grease. When these ingredients or feed with these ingredients are stored or processed, the fatty acids in them can become oxidized or rancid. In fact, restaurant grease is oftentimes oxidized even before it is received as a feed ingredient.
Oxidation can affect the palatability of the feed. Rancid fats and oils can have odd odors that are objectionable to pigs. Of course, if pigs eat less, they grow more slowly. But even when fats and oils are not so rancid that pigs won’t eat them, their presence in feed can be concerning. When they are ingested by pigs, systems in the body of the pig work to combat that oxidation and prevent their own tissues from being damaged. While dietary antioxidants can help combat this damage, they may not be perfect. Even the best dietary antioxidants can’t reverse oxidation that has already occurred in the feed.
How does oxidation impact pork quality?
Therein lies the concern about pork quality. If the pig is not completely able to combat the oxidation in feed, then the pork produced from that pig might start with a higher than normal amount of oxidation in its meat. Oxidation in meat, just like oxidation in feed ingredients, can result in off-odors and off-flavors. You might have experienced these flavors in foods if you have ever eaten stale chips or heated up some leftover French fries. As you can imagine, no one wants those flavors in their bacon or sausage. The other concern about oxidation in meat is that it can lead to browning during storage. Consumers tend to shy away from purchasing brown pork chops or sausage.
Because of these concerns, a series of studies have recently focused on feeding oxidized oils to pigs and assessed their effects on meat quality and shelf-life. Lucky for us, it was all pretty good news. Even when diets were quite high in oxidation, there were no overwhelmingly negative effects on pork chop quality and shelf life or bacon processing yields and quality. As I personally ate both pork chops and bacon from some of these studies, I can attest that there are no off-flavors and odors in the pork.
Oxidized feed ingredients will continue to be a concern for pig performance, but producers can rest assured that the pork they are producing, even when the feed may be oxidized, remains high quality and tasty.
Want to know more? You can find this research published by Martin Overholt, a student in my lab, in the Journal of Animal Science.
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