The Influence of Diet and Oxidation on Calcium Retention of the Mitochondria in Fresh Beef

Distillers grains (DG) contribute to cattle sarcoplasmic reticulum (SR) membrane instability by increasing poly-unsaturated fatty acid (PUFA) content in the SR membrane, possibly resulting in early postmortem calcium (Ca) leakage and improved tenderness. Mitochondria are relatively easy to isolate intact and provide the opportunity to study Ca in an SR model. The objective of this research was to determine the influence of diet and oxidation on Ca release from mitochondria. Cattle (n=48) were fed a corn-based finishing diet with or without deoiled, dried DG (50% DM basis). Steaks from each strip loin were aged for 2, 8, 14, and 21 days, powdered, and stored at -80oC for lab analysis. Samples (n=12) were randomly sub-sampled from each diet group for all aging periods. Mitochondria were isolated from day 2, 8, and 14 day-aged samples using high speed ultracentrifugation. The SR was isolated from each day 2 sample. Both mitochondria and SR samples were analyzed for PUFA content using gas chromatography, and phospholipid content using thin layer chromatography. Mitochondria from days 2 and 8 were artificially oxidized using an iron and ascorbic acid mixture. In both organelles, the DG diet samples had higher 18:2 and total PUFA content (P\u3c0.05) contents compared to day 2 and 8 mitochondria, as expected from aging of unsaturated fats. Phospholipid contents (phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol) of the mitochondria and SR were unaffected by diet. Oxidized mitochondria retained significantly less Ca than non-oxidized (P\u3c0.05) mitochondria. Day 2 mitochondria retained significantly less Ca than day 8 (P\u3c0.05) mitochondria. Overall, mitochondria from cattle finished on corn tended (P\u3c0.10) to retain more Ca than mitochondria from cattle finished on DG. Results indicate that greater PUFA content deposited in organelles by the DG diet may affect Ca flux by increased susceptibility to oxidation. A DG diet may influence Ca flux and ultimate tenderness by this mechanism. Advisor: Chris R. Calkin

Impact of Dietary Fat Source on Beef Display Life

This study was conducted to evaluate the effects of dietary fat source with modified distillers grains plus solubles (MDGS) on beef display life. Steers were fed either a corn control, full-fat MDGS, de-oiled MDGS, or de-oiled MDGS plus corn oil diet. Strip loins were aged for 2, 9, 16 and 23 days and placed under retail conditions for 7 days. Results suggest that feeding MDGS to cattle increases polyunsaturated fatty acid content of beef and has the potential to reduce beef color and lipid stability in comparison to corn diets. These data indicate that feeding MDGS to cattle may decrease beef display life. Addition of corn oil to de-oiled MDGS decreased redness and increased discoloration and lipid oxidation in comparison to corn control diets

The Relationship between Marbling, Superoxide Dismutase, and Beef Tenderness

This study was conducted to evaluate the relationships between animal oxidative status (as indicated by superoxide dismutase [SOD] activity) to marbling and beef tenderness. Prime and Select-grade strip loins were selected and aged for 2, 7, 14, 21, and 28 days for Warner Bratzler shear force, Troponin-T, and SOD activity. Results showed that meat exhibiting higher levels of marbling had lower shear force values and thus were more tender. Low-marbled samples tended to have a greater tenderness response to aging. The effect of oxidative stress, however, was not evident in this study as SOD values were similar. Although the effects of oxidative stress on beef tenderness are still unclear, results from this study provide a conceptual foundation for a new research perspective on meat tenderness

The Influence of Diet and Oxidation on Calcium Retention of the Mitochondria in Fresh Beef

Distillers grains (DG) contribute to cattle sarcoplasmic reticulum (SR) membrane instability by increasing poly-unsaturated fatty acid (PUFA) content in the SR membrane, possibly resulting in early postmortem calcium (Ca) leakage and improved tenderness. Mitochondria are relatively easy to isolate intact and provide the opportunity to study Ca in an SR model. The objective of this research was to determine the influence of diet and oxidation on Ca release from mitochondria. Cattle (n=48) were fed a corn-based finishing diet with or without deoiled, dried DG (50% DM basis). Steaks from each strip loin were aged for 2, 8, 14, and 21 days, powdered, and stored at -80oC for lab analysis. Samples (n=12) were randomly sub-sampled from each diet group for all aging periods. Mitochondria were isolated from day 2, 8, and 14 day-aged samples using high speed ultracentrifugation. The SR was isolated from each day 2 sample. Both mitochondria and SR samples were analyzed for PUFA content using gas chromatography, and phospholipid content using thin layer chromatography. Mitochondria from days 2 and 8 were artificially oxidized using an iron and ascorbic acid mixture. In both organelles, the DG diet samples had higher 18:2 and total PUFA content (P\u3c0.05) contents compared to day 2 and 8 mitochondria, as expected from aging of unsaturated fats. Phospholipid contents (phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol) of the mitochondria and SR were unaffected by diet. Oxidized mitochondria retained significantly less Ca than non-oxidized (P\u3c0.05) mitochondria. Day 2 mitochondria retained significantly less Ca than day 8 (P\u3c0.05) mitochondria. Overall, mitochondria from cattle finished on corn tended (P\u3c0.10) to retain more Ca than mitochondria from cattle finished on DG. Results indicate that greater PUFA content deposited in organelles by the DG diet may affect Ca flux by increased susceptibility to oxidation. A DG diet may influence Ca flux and ultimate tenderness by this mechanism. Advisor: Chris R. Calkin

Impact of Dietary Fat Source on Beef Display Life

This study was conducted to evaluate the effects of dietary fat source with modified distillers grains plus solubles (MDGS) on beef display life. Steers were fed either a corn control, full-fat MDGS, de-oiled MDGS, or de-oiled MDGS plus corn oil diet. Strip loins were aged for 2, 9, 16 and 23 days and placed under retail conditions for 7 days. Results suggest that feeding MDGS to cattle increases polyunsaturated fatty acid content of beef and has the potential to reduce beef color and lipid stability in comparison to corn diets. These data indicate that feeding MDGS to cattle may decrease beef display life. Addition of corn oil to de-oiled MDGS decreased redness and increased discoloration and lipid oxidation in comparison to corn control diets

The Relationship between Marbling, Superoxide Dismutase, and Beef Tenderness

This study was conducted to evaluate the relationships between animal oxidative status (as indicated by superoxide dismutase [SOD] activity) to marbling and beef tenderness. Prime and Select-grade strip loins were selected and aged for 2, 7, 14, 21, and 28 days for Warner Bratzler shear force, Troponin-T, and SOD activity. Results showed that meat exhibiting higher levels of marbling had lower shear force values and thus were more tender. Low-marbled samples tended to have a greater tenderness response to aging. The effect of oxidative stress, however, was not evident in this study as SOD values were similar. Although the effects of oxidative stress on beef tenderness are still unclear, results from this study provide a conceptual foundation for a new research perspective on meat tenderness