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By Jacquelyn Prestegaard, ASAS Communications

Oxidative stress, the imbalance of pro- and antioxidants, is highly detrimental to meat animal production. Excess oxidants damage animal cells and tissues and may ultimately impair animal health and growth. Also, diets that are high in oxidants negatively affect meat flavor, color, texture and nutritive value.

The process of converting the starch in grain, corn for example, into ethanol for biofuel has increased the availability of feed-grade co-products, such as dried distillers grains, and dried distillers grains have become a common ingredient in livestock diets. Dried distillers grains are rich in polyunsaturated fatty acids (PUFA), which are highly oxidative. Researchers in the pork industry are determining how to incorporate various antioxidants into diets containing dried distillers grains to mitigate the effects of oxidative stress.

“We became aware [of] reports [from farmers] of dietary-related oxidative stress and associated carcass problems in pigs,” said Dr. Allan Harper, Professor Emeritus of Animal Science at Virginia Tech. “The most profound cases had been reported in Asian production regions…but there were also related concerns in North American pork production settings with the increased use of dried distillers grains.”

To learn more about this, Harper and his research team at Virginia Tech fed varying amounts and types of antioxidants to pigs fed diets high in oxidants.

“We set up a dietary model that imposed a relatively high level of oxidative stress on the pig, similar to those from the Asian production regions,” said Harper. “[We] then attempted to remediate the performance, carcass and physiological aspects of the oxidative stress with either vitamin E or a commercial antioxidant.”

They summarize the results in two articles published in the December 2014 issue of the Journal of Animal Science. The first article examines the effects of antioxidant supplementation on pig growth, liver function and oxidative status. The second article takes a look at the impact on carcass characteristics, meat quality and fatty acid profile.

Here are some key findings from these two articles:

  • Pigs fed a diet high in oxidants, without any antioxidant supplementation, displayed such poor health that they were switched to a conventional corn-soy diet after 83 days on the trial. Their health improved, but the pigs’ daily gains still didn’t measure up to that of their peers fed the conventional diet. The diet high in oxidants also had negative effects on liver function.
  • The addition of vitamin E, a fat-soluble antioxidant, to a diet high in oxidants did not improve performance. In fact, pigs fed a diet high in oxidants and their peers fed the same diet but with added vitamin E both had light carcass weights, less back fat, less lean body mass and smaller loin eye area. There were a few perks, say the researchers, such as “some protective effects” of feeding vitamin E during the early growth phase of the pigs.
  • The addition of a commercial antioxidant blend (containing ethoxyquin and propyl gallate) to a diet high in oxidants improved the oxidative status of the pigs, but it did not prevent unfavorable color change in the loin or improve belly firmness (optimal firmness is important for bacon quality). However, pigs on this treatment showed greater feed efficiency than those fed the conventional corn-soy diet.
  • The addition of both vitamin E and a commercial antioxidant blend improved growth and liver function in pigs fed a diet high in oxidants, which is something the vitamin E alone did not do.

Overall, the addition of the antioxidant blend proved to be effective in improving the growth performance of pigs fed a high-oxidant diet.

“From a swine nutrition standpoint, I feel a key result of this work is that [a feed-grade antioxidant blend] including ethoxyquin…can also have a positive physiological impact in [an] animal that is already being exposed to dietary oxidative stress,” Harper said.


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