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The objective of this study was to evaluate the effects of dietary fat source with modified distillers grains plus solubles (MDGS) on beef tenderness through examination of sarcoplasmic reticulum (SR) membrane fatty acid composition, changes in sarcoplasmic calcium concentration, Warner-Bratzler shear force (WBSF), sarcomere length, and proteolysis early postmortem. Steers (n = 256) were fed for 134 d on either corn, or a diet containing 40% full-fat MDGS, 40% de-oiled MDGS, or 38% de-oiled MDGS plus 2% corn oil. Twenty-four USDA Choice carcasses (three carcasses per pen; eight pens per treatment) were selected within each dietary treatment, and strip loins were collected and aged for 2, 9, 16, or 23 d postmortem and subject to retail display (RD) for an additional 7 d. Feeding MDGS increased (P < 0.05) concentrations of linoleic acid (18:2) and tended to increase (P = 0.06) total polyunsaturated fatty acids (PUFA) in the SR membrane. Steaks from cattle fed MDGS had greater sarcoplasmic calcium concentration than steaks from cattle fed corn at day 2 postmortem (P = 0.05). Steaks from steers fed de-oiled MDGS and de-oiled MDGS plus corn oil tended to have lower WBSF values (P = 0.08) than steaks from cattle fed corn at 2 d of aging with 0 d of RD. There were no differences among dietary treatments for sarcomere length (P = 0.92) and troponin-T degradation at 2 d postmortem (P = 0.60). Results suggest that feeding MDGS may increase early postmortem release of calcium into the sarcoplasm due to increased 18:2 and PUFA concentration in the SR membrane, which could result in increased beef tenderness early postmortem.

The effects of feeding different dietary fat sources with modified distillers grains plus solubles (MDGS) on beef display life were evaluated. Steers (n = 256) were fed for 134 d on either a corn, 40% full-fat MDGS, 40% de-oiled MDGS, or 38% de-oiled MDGS plus 2% corn oil diet. Twenty-four United States Department of Agriculture Choice carcasses (3 head/pen) were randomly selected within each dietary treatment and strip loins were collected and aged for 2, 9, 16, or 23 d. Steaks from each aging period were placed under retail display (RD) conditions for 0, 4, and 7 d. Stearic acid was predominant (C18:0; P = 0.03) in beef from the de-oiled MDGS plus oil treatment in comparison with all other dietary treatments. Feeding MDGS increased linoleic acid (C18:2; P < 0.01) and polyunsaturated fatty acids (PUFA; P = 0.01) in comparison to the corn diet. The de-oiled MDGS plus oil group had greater C18:3 content (P = 0.03) when compared to corn, but no differences were observed between all other diets. There were no differences among dietary treatments for L* (P = 0.74) and b* (P = 0.25) values. The de-oiled MDGS group had lower a* values than all other treatments (P < 0.01) at day 5 of RD. The corn treatment had greater a* values (P ≤ 0.05) than de-oiled MDGS and de-oiled MDGS plus oil at day 6 and 7 of RD. Strip loin steaks from cattle fed full-fat MDGS tended to have lower a* values (P = 0.10) than steaks from cattle fed corn at day 7 of RD. Feeding de-oiled MDGS resulted in greater discoloration (P ≤ 0.05) at days 5, 6, and 7 of RD when compared to corn. Steaks from the de-oiled MDGS plus oil and full-fat MDGS groups had greater discoloration scores at day 7 of RD in comparison to corn (P ≤ 0.05). Strip loin steaks from cattle fed corn tended to have lower thiobarbituric acid reactive substance (TBARS) values (P ≤ 0.10) in comparison to de-oiled MDGS and de-oiled MDGS plus oil at day 7 of RD. Results suggest that feeding MDGS to cattle reduces color and lipid stability in addition to increasing C18:2 and PUFA content of beef. Addition of corn oil to de-oiled MDGS decreased redness and increased discoloration and lipid oxidation in comparison to corn diets.

Feeding wet distillers grains plus solubles (WDGS) in beef feedlot diets increases beef polyunsaturated fatty acids (PUFA) concentration and decreases shelf-life; whereas feeding antioxidants like vitamin E and Agrado-Plus (AG; an ethoxyquin and tert-Butylhydroquinone mixture) mitigates such effects. The objective of this study was to evaluate shelf-life of beef from steers supplemented with WDGS and different antioxidants. One hundred and sixty steers were finished on a corn-based diet with 0% WDGS or 30% WDGS and four antioxidant treatments (no supplementation; vitamin E only; AG only; vitamin E + AG). Ten strip loins from each treatment were collected, aged, cut into steaks, and placed under retail display (2 ± 2°C). During retail display, steaks were evaluated daily for objective colour and subjective discolouration. After retail display, steaks were used to measure lipid oxidation, muscle fatty acids, and vitamin E and ethoxyquin concentrations. Feeding 30% WDGS increased total PUFA in beef when compared with beef from steers fed 0% WDGS (P < 0.05). Supplementing vitamin E or vitamin E + AG was effective in decreasing myoglobin and lipid oxidation in steaks from steers fed 0% or 30% WDGS after retail display (P < 0.01). Supplementation of vitamin E or AG also increased (P < 0.01) muscle tissue vitamin E or ethoxyquin levels, respectively, compared with the diets without vitamin E or AG supplementation. The inclusion of 30% WDGS altered beef fatty acid profiles, but did not promote lipid and myoglobin oxidation compared with the 0% WDGS diet. Feeding vitamin E was effective, whereas supplementing AG had minor effects in decreasing myoglobin and lipid oxidation in steaks from both diet.