Investigation of Blood Selenium Status of Dairy Cattle Herds in Isfahan Province Industrial Cattle Farms

Selenium is an essential element in dairy cattle, particulrarly for reproduction. The present study was conducted in order to determine the amount of selenium in the blood of different groups of cattle in Isfahan province industrial cattle farms and also the effect of season (summer and winter) on its concentration in the form of a randomized complete block design. The present study was investigated the blood selenium level in dairy cattle in Isfahan province. Also, the effect of season (summer and winter) on selenium values was studied. This experiment was carried out in a complete block randomized design for 553 cows in 17 farms from different regions of the Isfahan province. Acordingly, 553 cows were selected from 17 industrial cattle breeding units in different geographical parts of the province. The population of cows in each cattle farm wasere divided into five groups which included high producing cows (n=154), fresh cows (n=118), dry and pregnant heifers (n=121), non-pregnant heifers (n=81) and calves. Blood selenium concentration was indirectly assessed determined through the measurement of glutathione peroxidase activity by Alpha Classic Auto Analyzer. According to the results, the mean whole blood selenium concentration mean for high producing cows, fresh cows, dry and pregnant heifers, non-pregnant heifers and calves were measured at 0.21, 0.18, 0.24, 0.24, 0.21 mg/L, respectively. Dry and pregnant heifers and non-pregnant heifers with higher selenium concentration showed significant differences compared to other groups (P<0.05). The lowest selenium concentration was significantly observed for fresh cows (P<0.05). No significant differences were found among different groups of dairy cows in terms of peroxidase enzyme activity for glutathione peroxidase activity. The mean blood selenium concentrations in summer and winter with no significant differences were at 0.21± 0.08  (n=129) and 0.20±0.06  (n=174) mg/L, respectively which showed no significant effect of season on blood selenium level. Also, the comparison of the same group in different farms showed significant difference in terms of blood selenium levels s between them (P<0.05).Therefore, it is recommended to check the blood selenium level of dairy cattle and then ,use a selenium supplement under supervision of animal nutritionists.