AbstractsChemistry

White muscle disease or muscular dystrophy of sheep is a selenium responsive malady common to many areas with an inherent natural deficiency of selenium in the forage. The disease can be prevented in lambs by adding trace amounts (approximately 0.1 ppm) of selenium to the otherwise selenium deficient, forage fed to their dams prior to birth. It has been previously reported that the lambs afflicted with muscular dystrophy as a consequence of selenium deficiency exhibit a marked elevation of 5'-nucleotidase, a specific alkaline phosphatase, in semitendinosus muscle tissue. In order to determine what the relationship of dietary selenium to 5'-nucleotidase activity might, be, ewes were randomly divided into five lots which included a control group receiving selenium adequate forage, a basal group receiving selenium deficient forage, and three groups receiving the basal ration plus the following respective selenium supplements administered as sodium selenite: 0.1 ppm selenium in the ration, 30 mg. selenium orally in 10 mI. water, and 30 mg. selenium in wax parentally. At six weeks of age, the lambs from these ewes were slaughtered and the semitendinosus muscle removed and frozen for subsequent enzyme assays. The results of the 5'-nucleotidase assay indicated a marked elevation of enzyme in dystrophic muscle from 1.6 to 6.6 times the mean of the control muscle. However, the lambs from the selenium treated dams all reflected lower 5'-nucleotidase activity from the controls although the differences were not statistically significant. The enzyme activity was expressed as micromoles inorganic phosphate released per hour per mg. nitrogen in the muscle extract. The optimal conditions of the assay included an hour's incubation at 38°C. at a pH of 8.3. Neither the mechanism of 5'-nucleotidase enhancement, in dystrophic lamb muscle nor the effect, of selenium upon repressing activity levels is immediately apparent, although various possibilities and explanations are discussed.