Use of 25-hydroxyvitamin D3 and vitamin E and manipulation of dietary calcium to improve tenderness of beef

The objective of this trial was to determine whether a single bolus of 25hydroxyvitamin D3 (25-OH D3), vitamin E, or a combination of the two would improve the tenderness of steaks from the longissimus dorsi of beef heifers. Forty-eight Angus cross heifers were allotted randomly to 8 pens. Six heifers were in each pen, and there were two pens per treatment. The four treatments included Control, no 25-OH D3 or vitamin E; 25-OH D3, 500 mg of 25-OH D3 administered as a one-time oral bolus 7 d before harvest; Vitamin E, 1000 IU of vitamin E administered daily as a top-dress for 104 d before harvest; or Combination, 500 mg of 25-OH D3 administered as a one-time oral bolus 7 d before harvest and 1000 IU of vitamin E administered daily as a top-dress for 104 d before harvest. Blood samples were obtained on the day that heifers were allotted to treatments, on the day 25-OH D3 was administered, and on the day before harvest. Plasma calcium concentration was increased in plasma when 25-OH D3 was administered with or without vitamin E (P < 0.007). In longissimus dorsi muscle, calcium concentration tended to increase (P = 0.10) when 25-OH D3 was administered alone but not when 25-OH D3 was administered with vitamin E. Concentrations of 25-OH D3 and 1,25-dihydroxyvitamin D3 (1,25-(OH)2 D3) in plasma were increased when 25-OH D3 was administered with or without vitamin E (P < 0.001). Steaks from heifers treated with 25-OH D3 or vitamin E, but not both, tended to be more tender than steaks in the control group after aging for 14 d (P = 0.08). Postmortem protein degradation as measured by western blot of the 30-kDa degradation product of troponin-T was increased with all treatments after 3 d of aging, but at 7 and 14 d there were no changes. Overall, use of 500 mg of 25-OH D3 fed as an oral bolus 7 d before harvest or 1000 IU of vitamin E