Start Date: Mar 01, 2013
End Date: May 31, 2014
Objective 1. The standard laser diffraction method of sarcomere length measurement will be compared to a protocol for obtaining high quality micrographs of powdered muscle tissue allowing images of sarcomeres to be captured for image analysis measurement of sarcomere length on 100 longissimus samples ranging widely in tenderness. Objective 2. Slice shear force will be determined on longissimus from 1000 carcasses of steers sired by bulls from each of the 16 most prevalent beef breeds in the U.S. beef herd. Sarcomere length and degradation of the cytoskeletal protein desmin using western blotting will be measured on each sample. Objective 3. Carcasses (n = 30) will be selected to be variable in tenderness. Five muscles (longissimus lumborum, semimembranosus, biceps femoris, vastus lateralis, semitendinosus) will be obtained from each carcass and cut into five steaks which will be aged until 2, 5, 7, 14, and 28 d postmortem. Steaks will be cooked and slice shear force determined to assess tenderness and postmortem proteolysis will be determined by western blotting.