Tenderness is one of the most important quality characteristics of beef to both consumers and producers. To date, no practical method of producing consistently tender beef has been adopted by the beef industry. Researchers have demonstrated that feeding a supernatural dosage (0.5 to 7.5 million IU) of vitamin D3 to beef cattle for 7 to 10 days before slaughter will result in more tender carcasses (Swanek et al., 1999; Montgomery et al., 2000; Montgomery et al., 2002; Karges et al., 2001). Feeding this amount of vitamin D3 results in elevated plasma and muscle calcium concentrations (Swanek et al., 1999; Montgomery et al., 2000; Montgomery et al., 2002; Karges et al., 2001). The assumed mechanism for this tenderization effect is that the elevated muscle calcium concentration enhances the action of the calcium-dependent protease system of myofibrillar (troponin-T) protein degradation postmortem. Enhanced myofibrillar protein degradation results in more tender beef that is more desirable to consumers. For producers, being able to produce a “guaranteed tender” product even may warrant a price premium.