Feeding Vitamin E May Reverse Sarcoplasmic Reticulum Membrane Instability Caused by Feeding Wet Distillers Grains Plus Solubles to Cattle

Abstract Text: Feeding wet distillers grains plus solubles (WDGS) in beef feedlot diets increases polyunsaturated fatty acid (PUFA) concentration in the sarcoplasmic reticulum (SR) membrane, thereby altering membrane integrity, resulting in more rapid post-rigor calcium leakage and improving tenderness through early activation of calcium dependent proteases. Supplementation with antioxidants may mitigate such effects. One hundred and sixty cross-bred steers were finished on either corn or 30% WDGS with 4 antioxidant treatments [none – control; vitamin E (VitE) at 450 mg (1,000 IU)/hd/d; Agrado Plus (Ag) at 3 g/hd/d (215 ppm of feed); a combination of 225 mg (500 IU)/hd/d of VitE and 3 g/hd/d of Ag]. Ten strip loins from each treatment (n=80) were aged for 2, 7, and 14 d.  Steaks from each aging period were placed under retail display conditions for 0, 4, and 7 d. Discoloration, tenderness (WBSF), free calcium concentrations, lipid oxidation, sarcomere lengths, proteolysis, and SR lipid, phospholipid and fatty acid profiles were measured. Feeding VitE was effective in reducing (P < 0.01) lipid oxidation for all three display periods in beef from cattle fed corn and was effective in maintaining color stability after 6 d of retail display (P < 0.01) in beef from both corn and WDGS diets. Without antioxidant supplementation, there were no differences in discoloration scores between the two dietary treatments for any of the aging and display periods, but steaks from corn-fed steers had higher lipid oxidation values at all three display periods compared to steaks from steers fed 30% WDGS. Feeding WDGS decreased (P < 0.01) total saturated fatty acids in the SR membrane, tended to decrease (P = 0.09) total monounsaturated fatty acids, and increased (P = 0.01) total PUFA. Furthermore, steaks from steers fed WDGS had more (P < 0.05) phosphatidylcholine in the SR membrane, but less (P < 0.05) phosphatidylethanolamine compared to steaks from steers fed corn or WDGS supplemented with VitE. There were no differences in tenderness, sarcomere length, or free calcium concentrations among steaks from steer in any of the treatments, aging and display periods. At 2 d postmortem, steaks from steers fed WDGS had more proteolysis compared to steaks from steers fed corn only or WDGS supplemented with VitE. These results suggest that the alteration of SR fatty acid profile in WDGS fed cattle may affect the ratio of SR membrane phospholipids, and thus contribute to differences in proteolysis. Feeding VitE mitigates such effects.

Keywords: Distillers grains, sarcoplasmic reticulum, fatty acids