Muscle calcium modulation using vitamin D to improve beef tenderness



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Texas Tech University


The effect of supplemental vitamin D3 (VITD) doses during the last 8 d of feeding and biological type of cattle on feedlot performance, VITD residues, meat tenderness, and muscle calcium homeostasis was studied. Supplementing cattle with 5 million lU/steer daily of VITD negatively affect average daily gain and feed intake, but feeding 1 or .5 million lU/steer daily did not negatively impact feedlot performance data. All the treatments studied improved meat tenderness. Sensory panel scores and Warner-Bratzler shear force indicated that the longissimus and semimembranosus muscles were the most responsible to VITD improving tenderness by as much as 21%. Tissue VITD residues in the liver, kidney, and muscle were increased by supplementing steers with VITD. Cooking samples seemed to reduce treatment effects on residues. Supplementing steers with VITD also increased the calcium content of meat and activated ì-calpain, thereby increasing myofibrillar proteolysis and degradation of troponin T. Therefore, vitamin D supplementation of beef cattle can improve meat tenderness and presumably improves the marketability of beef by decreasing the variation in beef tenderness and accelerating postmortem tenderization.

The effect of VITD supplementation on muscle mineral metabolism also was investigated. The VITD treatments seemed to increase the binding of calcium near the Zline and to myofibril proteins. Moreover, VITD supplementation and postmortem aging increased the concentration of Ca2+and P in the cytosol of longissimus muscle.

Several cell culture experiments were devised to try and explain the role of vitamin D in muscle cell protein synthesis and degradation. Treatment of myotubes with l.25-dihydroxyvitamin D3 decreased cellular protein synthesis and increased cellular protein degradation. The expression of calpastatin, m-calpain, calbindin, and the calcium-sensing receptor also were decreased by treatment in myotubes. Therefore, the affects of VITD treatment on cellular degradation might be attributable to regulation of calpastatin, ì-calpain, and m-calpain expression.

Therefore vitamin D3 is an important regulator of calcium homeostasis and proteolysis in muscle. Feeding vitamin D3 at .5 million lU daily for 8 d to steers can improve beef tenderness and possibly the marketability of beef