#10-002

Complete

Date Full Report Received

04/23/2012

Date Abstract Report Received

04/23/2012

Investigation

Institution:
Primary Investigator:
Background: Oxidative damage in feedstuffs represents a significant economic loss because it negatively affects pig health and growth performance. Lipid peroxidation occurs during the production of corn dried distillers grains with solubles (DDGS). Corn oil, which is typically present at a concentration of 10% in DDGS, contains high levels of polyunsaturated fatty acids, particularly linoleic acid, which are vulnerable to lipid peroxidation. Increased drying time and temperature used by ethanol plants accelerates lipid peroxidation in DDGS. It appears that that feeding diets containing DDGS with oxidized fat to pigs may require supplementation of higher levels of antioxidants (e.g. vitamin E) than currently being fed. Improved growth performance was reported in one study when pigs were fed diets containing DDGS or oxidized corn oil supplemented with antioxidants, but results from other studies have shown that supplementation of antioxidants had no effect on growth performance in animals under a dietary oxidative stress challenge. Therefore, one of the objectives of this study was to evaluate the effects of feeding a diet containing DDGS with a high content of oxidized lipids and sulfur on pig growth performance and metabolic oxidation status, and to determine if any of the negative effects could be overcome by increasing dietary level of vitamin E. Sulfur-containing compounds, including methionine, cysteine, taurine, and glutathione, have been shown to have potent antioxidant properties, and DDGS often containa high concentrations of sulfur due to the large amount of sulfuric acid added during the ethanol production process. There is no published information available regarding sulfur-containing antioxidants in response to feeding DDGS with high sulfur content to pigs, nor if sulfur-containing compounds produced by pigs could protect them against lipid peroxidation induced by feeding DDGS. Therefore, we were also interested in determining whether the high sulfur content in DDGS could protect against lipid peroxidation in pigs fed DDGS diets.

Objectives: To determine the nutrient content and lipid oxidation levels in DDGS samples from different sources and investigate the effects of feeding diets containing oxidized DDGS, with and without an antioxidant, on growth performance, health and immune status, nutrient digestibility, and metabolic oxidation balance in nursery pigs.

Procedures: The DDGS source used in this study was selected out of 31 DDGS sources produced by the ethanol plants in the U.S., and contained the highest thiobarbituric acid reactive substances (TBARS) value, peroxide value, and total sulfur content (5.2 ng/mg oil, 84.1 meq/kg oil, and 0.95%, respectively) among the other 30 DDGS sources sampled (mean values = 1.8 ng/mg oil, 11.5 meq/kg oil, and 0.50%, respectively). Fifty-four barrows were fed corn-soybean meal (CON) or 30% DDGS diets containing one of 3 levels of vitamin E (α-tocopheryl acetate): none supplemented (No-E), NRC (1X-E), or 10X NRC (10X-E) using a 3-phase nursery feeding program with targeted body weight of 7-11 kg, 11-25 kg, and 25-50 kg for Phase 1, 2, and 3, respectively. Barrows were housed in pens and fed the experimental diets for 8 wk after weaning and transferred to individual metabolism cages for collection of feces, urine, blood, and liver samples.

Findings: Total sulfur content was higher in DDGS diets than CON (0.39 vs. 0.19%). Dietary inclusion of 30% DDGS improved apparent total tract digestibility of sulfur (86.8 vs. 84.6%), as well as sulfur absorbed and retained compared to CON. Although pigs were fed highly oxidized DDGS in this study, serum TBARS were similar between DDGS and CON treatments. There was no interaction between dietary DDGS and α-tocopherol concentration in serum TBARS. Serum α-tocopherol (vitamin E) increased by feeding DDGS diets compared to CON (2.25 vs. 1.56 µg/mL). In addition, pigs fed DDGS diets had higher concentrations of sulfur-containing amino acids, particularly methionine and taurine in serum of fed pigs, and a higher concentration of taurine in serum of fasted pigs compared with those fed CON. Liver glutathione concentration was higher in pigs fed DDGS diets than CON (56.3 vs. 41.8 nmol/g). Dietary inclusion of DDGS and α-tocopherol increased serum enzyme activity of glutathione peroxidase.

Conclusions: The elevated concentrations of sulfur-containing antioxidants (methionine, taurine, glutathione) may protect pigs against oxidative stress when feeding highly oxidized DDGS. Therefore, increasing levels of α-tocopherol (vitamin E) in diets containing DDGS with high oxidized lipid content may not be necessary to protect pigs from metabolic oxidation stress.