Vitamin E selenium deficiency Bovine calves
In suckling calves and weaned calves pathology is more outspoken in skeletal muscles used in physical activities. Suckling animals = tongue and neck muscles. In older calves = skeletal muscles and / or cardiac muscle. Extensive cardiac involvement (usually left ventricular) is frequently accompanied by lesions in intercostal muscles and diaphragm (see gross images right) but other skeletal muscles are not affected to the same degree. Histological lesions are multifocal with lesions of various duration evident (polyphasic myopathy). Early changes are of hypercontraction band formation with hyaline degeneration followed by necrosis and myofibre cytolysis. Mineralization of necrotic fibres is common in calves (histo image below). Influx of inflammatory cells (macrophages and mononuclear cells) to clean up necrotic debris and replacement fibrosis follows.