Gastrocnemius muscle rupture associated to selenium deficiency in beef cattle.

Three cases of gastrocnemius muscle rupture occurred in cattle. The first two cases (Cases 1 and 2) occurred in a herd of 128, 16-18-month-old crossbred steers in Argentina; the lesions were bilateral. A third case (Case 3) occurred in a herd of 20, 2-year-old crossbred heifers in Uruguay; the lesion was unilateral. The three animals showed the tarsal joints flexed at an ~ 90° angle and the metatarsal bone region was touching the ground along its entire length. Necropsy and histopathology were conducted on Cases 1 and 3. Grossly, the gastrocnemius muscles were torn and edematous. Microscopically, the two animals had polyphasic, multifocal muscle necrosis with proliferation of satellite cells and macrophage infiltration. In Case 3 the selenium liver concentration was 0.29 ppm DW; selenium concentration was not measured in Cases 1 and 2. The gross and microscopic changes, coupled with low concentration of selenium in one of the animals, suggests that the gastrocnemius rupture was consequence of nutritional myopathy associated with selenium deficiency.