Abstract
Thirty five cows with an average age of 5. 6 years were pastured in two different public Experimental Stations from spring to autumn and reared indoors on supplemental commercial formula feed throughout winter. Samples of grass, blood and hair were collected at the beginning and end of the grazing period to investigate the effect of grazing on the nutritional status of selenium (Se) in cows. Se content of mixed pasture showed fairly low values ranging from 0. 019ppm to 0. 032ppm. No apparent difference in Se content was observed according to sampling site, species and season. Values of either blood or hair Se concentration were significantly (P<0.01) lower in autumn than in spring but were still all within the normal range according to that previously reported for Se deficient animals. The increase in serum enzymes, GOT and LDH, was not as great as that reported in nutritional muscular dystrophic animals. It was considered that the Se status of cows grazed in summer season may be free from deficiency, though it becomes fairly low during pasturing.
