Impact of diet and quality grade on tenderness of beef steaks

Research was conducted to evaluate the effects of feeding different types of processed corn, with or without distiller grains with solubles, and differing quality grade on tenderness of beef steaks. Steers (n=240) were finished on Dry Rolled Corn (DRC), DRC + 30% Dried Distillers Grains with Solubles (DDGS), Steam Flaked Corn (SFC), or SFC + 30% DDGS. Cattle were fed 10 per pen. Only pens with upper 2/3 Choice and Selectgrade carcasses were sampled, with a goal of two (and a minimum of one) of each grade per pen. Three pens per treatment met the selection criterion and 36 carcasses were chosen (21 upper 2/3 Choice and 15 Select). Pen was considered the experimental unit. Both strip loins were collected from each carcass, halved, and aged for 2, 9, 16, or 23 d. After aging, steaks were placed under retail display for 7 d. Warner-Bratzler shear force (WBSF), slice shear force (SSF), sarcomere length, sarcoplasmic calcium, and troponin-T (TnT) degradation were determined. Minimal to no impacts on sarcomere length and calcium were found (P >0.05). For both WBSF and SSF, Choice steaks were more tender than Select. Significantly more Tn-T was degraded at 23 d of aging compared to 2 d of aging. Beef steaks from cattle fed DRC were more tender than SFC, regardless of the presence or absence of DDGS. For 2 d aged samples, Tn-T degradation was higher when cattle were fed DDGS compared to no DDGS. Overall, these data suggest that steaks from cattle fed DRC are more tender than steaks from cattle fed SFC and Choice-grade steaks are more tender than Selectgrade steaks.