Author
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MONTGOMERY, J - TEXAS TECH UNIV. |
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BLANTON, JR, J - TEXAS TECH UNIV. |
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Horst, Ronald |
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GALYEAN, M - TEXAS TECH UNIV. |
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MORROW, JR, K - TEXAS TECH UNIV. |
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ALLEN, V - TEXAS TECH UNIV. |
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WESTER, D - TEXAS TECH UNIV. |
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MILLER, M - TEXAS TECH UNIV. |
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Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/9/2004 Publication Date: 9/20/2004 Citation: Montgomery, J.L., Blanton, Jr, J.R., Horst, R.L., Galyean, M.L., Morrow, Jr, K.J., Allen, V.G., Wester, D.B., Miller, M.F. 2004. Effect of supplemental vitamin D3 concentration on concentrations of calcium, phosphorus, and magnesium relative to protein in subcellular components of the longissimus and the distribution of calcium within longissimus muscle of beef steers. Journal of Animal Science. 82(9):2742-2749. Interpretive Summary: We have shown that creating 20-30% elevation in blood calcium by feeding excess vitamin D several days prior to slaughter results in a tenderizing effect on meat. We used this approach to study the effect of supplementing diets with four levels of vitamin D3 [0, 0.5, 1, and 5 million IU/(steer/d) for 8 d] before slaughter on the mineral content and localization of calcium in muscle fragments. Our results indicate that vitamin D supplementation and postmortem aging both dramatically affect the ratio of calcium, phosphorus, and magnesium concentrations to protein in muscle and meat. Feeding vitamin D3 at 0.5 to 5 million IU/(steer/d) increased the ratio of calcium in cellular components in muscle, which was then released during postmortem aging and rigor development, increasing the ratio of calcium to protein in muscle cells. Improvements in meat tenderness with vitamin D3 supplementation might be explained by an increase in the calcium content within the respiring muscle cell which results in activation of protein breakdown. This research will benefit beef producers and beef nutritionists worldwide. Technical Abstract: The effect of supplementing steers with varying levels of vitamin D3 (VITD; 0, 0.5, 1, and 5 million IU/(steer/d)) on the mineral content and localization of Ca in longissimus muscle and muscle fragments was studied during the postmortem aging process. Differential centrifugation techniques were used to determine the distribution of minerals in different muscle fragments. Electron microscopy visualization of bound Ca indicated that all levels of VITD mobilized Ca from the sarcoplasmic reticulum and transverse tubule system into the myofibrils compared with controls. Bound Ca was concentrated near the Z-line at the A-band, I-band juncture within the sarcomere. Supplementing steers with 1 and 5 million IU/(steer/d) of VITD increased (P less than 0.05) the Ca2+, P, and Mg concentration in the cytosol. Soluble cytosolic Ca2+ concentrations increased over the aging treatment from d 3 to 21 postmortem only when steers were supplemented 5 million IU/d. Bound Ca, Mg, P, and Al concentrations were increased (P less than 0.05) in nuclei and myofibrilar proteins when samples were from steers supplemented with 1 and 5 million IU of VITD/d. Supplementing steers with all the levels of VITD also increased Mg concentrations in the cytosol regardless of aging treatment, and bound Mg concentrations within the mitochondria at d 3 postmortem. Soluble cytosolic Al concentrations increased (P less than 0.05) at 21 d postmortem only when steers were supplemented 5 million IU/d. Therefore, we conclude that the supplementation of feedlot steers with VITD at levels of 0.5 to 5 million IU/d increased Ca metabolism within the live muscle, resulting in increased bound Ca. When the muscle is converted to meat, increased bound Ca concentrations resulting from VITD treatment increased free cytosolic Ca2+ concentrations with increasing length of aging (P less than 0.05). This study indicates that VITD supplementation increases cytosolic Ca2+, P, Mg, and Al in meat. |
