Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Animal Science

First Advisor

Donald C. Beitz


Tenderness is one of the most important quality characteristics of beef. Inconsistent tenderness of beef costs the U.S. beef industry millions of dollars annually. Therefore, a practical method of improving tenderness could increase consumer satisfaction and willingness to purchase beef, which could lead to increased profits to producers. Calpain, the enzyme responsible for postmortem proteolysis, is calcium-dependent; so, increasing intracellular calcium concentrations presumably will result in increased proteolysis and, subsequently, more tender beef. We hypothesized that 500 mg of 25-hydroxyvitamin D3 (25-OH D3) administered as a single oral bolus seven days before harvest would increase calcium concentrations in plasma and in beef and lead to increased postmortem proteolysis and improved beef tenderness. Two studies were conducted to examine the effectiveness of 25-OH D3. One study combined the use of 25-OH D3 and vitamin E to improve tenderness of beef. Forty-eight Angus cross heifers were allotted randomly to one of four treatments. Five hundred milligrams of 25-OH D3 and vitamin E (1000 IU daily for 104 days before harvest) both improved tenderness; effects of the treatments, however, were not additive. Interestingly, vitamin E seemed to improve vitamin D status even when administered alone. The second study was designed to determine the effect of 25-OH D3 and withdrawing and then replenishing supplemental dietary calcium on tenderness of beef. Twenty-seven Angus cows were allotted by weight to one of nine dietary treatments arranged as a 3 [25-OH D 3 (0, 250, or 500 mg)] x 3 [supplemental dietary calcium (replenished at 0.50, 0.75, or 1.0% of diet dry matter)] factorial design. Seven muscles from the round were analyzed for indicators of tenderness. Calcium concentration in plasma and in muscle increased with 25-OH D3 supplementation, and postmortem proteolysis was increased in some muscles accordingly. Withdrawing and then replenishing supplemental dietary calcium did not affect calcium concentrations in plasma or in muscle, but in some muscles, postmortem proteolysis was increased when limestone was replenished at 1% of dietary dry matter. No significant improvement in tenderness was observed when treatments were applied to cows. In summary, dietary 25-OH D3 and vitamin E show promise as practical methods of improving beef tenderness.



Digital Repository @ Iowa State University,

Copyright Owner

Kristen Marie Carnagey



Proquest ID


File Format


File Size

120 pages