Abstract. Feeding wet distillers grains plus solubles (WDGS) increases polyunsaturated fatty acid (PUFA) levels in beef. It was hypothesised that WDGS in feedlot diets increases PUFA concentration in the sarcoplasmic reticulum (SR) membrane, thereby altering membrane integrity, resulting in more rapid intracellular calcium leakage and improved tenderness. The objective of this study was to evaluate this hypothesis. Ninety-six crossbred steers were fed either a corn-based diet with 0% WDGS or 50% WDGS. Fifteen strip loins per treatment were collected, fabricated into steaks, aged and placed under retail display conditions. Steaks were used to measure tenderness, proteolysis, free calcium concentrations, lipid oxidation, sarcomere length and SR membrane fatty acid, phospholipid lipid, neutral lipid and total lipid profiles. Compared with steaks from steers fed 0% WDGS, steaks from steers fed 50% WDGS were more tender (P < 0.05) and had greater (P < 0.05) free calcium concentrations early post-mortem. Feeding 50% WDGS also tended to increase (P < 0.10) total PUFA concentrations, decrease (P < 0.10) total phospholipid concentration and increase (P < 0.10) total neutral lipid concentration for SR membrane. Steaks from steers fed 0% WDGS had greater (P < 0.05) lipid oxidation (TBARS values) than steaks from steers fed 50% WDGS after extended aging. Although differences in tenderness between the two treatments were detected, there were no corresponding differences (P > 0.10) in sarcomere length or proteolysis. This study showed that feeding WDGS may increase tenderness, possibly by increasing free calcium in muscle early post-mortem. However, the true mechanism that contributes to these differences is still unclear.
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.
Research has shown feeding wet distillers grains plus solubles (WDGS) in beef feedlot diets increases PUFA concentration in the sarcoplasmic reticulum (SR) membrane, thereby altering membrane integrity, resulting in more rapid postmortem calcium leakage and improving tenderness through early activation of calcium-dependent proteases. Supplementation with antioxidants may mitigate such effects. A total of 160 steers were finished on a corn-based diet with 0 or 30% WDGS and 4 antioxidant treatments [no supplementation; vitamin E; Agrado; vitamin E plus Agrado]. Ten strip loins from each treatment were collected, aged, cut into steaks, and placed under retail display. Tenderness, free calcium, sarcomere lengths, proteolysis, and SR membrane phospholipid and fatty acid profiles were measured. The 30% WDGS diet increased (P < 0.05) total PUFA in the SR membrane. Steaks from steers fed 30% WDGS without an antioxidant had more (P = 0.05) phosphatidylcholine in the SR membrane but less (P < 0.05) phosphatidylethanolamine compared with steaks from steers fed 0% WDGS only or 30% WDGS supplemented with vitamin E. At 2 d postmortem, steaks from steers fed 30% WDGS had more (P < 0.05) proteolysis compared with steaks from steers fed 0% WDGS. There were no differences in tenderness, sarcomere length, or free calcium among treatments in any of the aging or display periods (P > 0.10). These results suggest that the alteration of SR membrane fatty acid profile in WDGS-fed cattle may affect the ratio of SR membrane phospholipids, creating membrane instability, and thereby increasing proteolysis, whereas feeding vitamin E mitigates such effects.
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.
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