Effect of production factors on muscle fiber type and dimensions in the m. semimembranosus of crossbred steer carcasses


  • Anusha Sivakumar WISEST student researcher, University of Alberta
  • Patience Coleman Faculty of Agriculture, Life and Environmental Sciences, University of Alberta
  • Bimol C Roy Faculty of Agriculture, Life and Environmental Sciences, University of Alberta
  • Heather L Bruce Faculty of Agriculture, Life and Environmental Sciences, University of Alberta




cattle, alberta, muscle fiber staining


The muscle fibers that have been examined in the study were affected by three different controlled factors: steroids, ractopamine and residual feed intake (RFI). By examining the effects of the controlled factors on cattle’s muscle fibers, it can be determined if they affect different meat properties, such as meat toughness, collagen solubility and muscle fiber quality. The research had been done specifically with m. semimembranosus (SM) of crossbred steers. Although some may be concerned with the health effects of steroids and other materials, no negative effects to the health of the cattle were observed after the use of steroids. This is because the hormones being introduced into the cattle’s body already exist in the animal. In addition, the same concept applies to humans who consume the meat, preventing harm the people who consume it. For this study, 48 crossbred angus steers were used, 12 for each of the different treatment groups. The control group consisted of no steroids and no ractopamine. The second group was not treated with steroid but with ractopamine. The third group was treated with steroids but no ractopamine. Finally, the fourth group was treated with both, the steroids and the ractopamine. For each SM muscle, 1-inch thick steaks were cut and from those steaks, 1cm3 cubes were cut. These cubes were frozen in dry ice acetone until they are ready to be sectioned. Cubes are placed in the cryostat and sliced into serial sections of 10µm. These serial sections are then mounted onto dry slide glass and stored in a freezer at -80ºC until they are to be stained. The staining process helps to identify the different types of muscle fibers in the samples. From the muscle fiber types, the average sizes of each muscle fiber is calculated to identify inconsistencies among the different treatment groups. Conclusions will be drawn based on the inconsistencies found (if any).