Abstract
A 2-year-old Holstein-Friesian cow with posterior weakness and an apparently normal 3-year-old Murray Grey steer were pathologically found to have steatosis in the skeletal muscles at meat inspection. In the Holstein-Friesian case, almost all the skeletal and diaphragmatic muscles of the carcasses contained considerble adipose tissue, whereas the trapezius muscle only was involved in the Murray Grey case. In both cases, steatotic lesions were distributed bilaterally and symmetrically without noticeable reduction in the original muscle volume. Microscopic feature common to the affected muscles in both cases was replacement of muscle fibers by fat cells, being so extensive as to reveal nearly complete absence of muscle fibers in some fascicles. Degenerative/necrotic muscle fibers were scattered in the recognizable muscle tissue. Frequently muscle fiber alteration as characteristic of denervation, showing sharply angulated or flattened atrophied muscle fibers, arranged singly or in small groups occasionally in association with internal nuclei or apparently increased number of nuclei. Neither regenerated muscle fibers nor proliferation of the stromal connective tissue were found.
