This study was conducted to evaluate seasonal concentrations of macro-minerals in serum or plasma of sheep under grazing conditions to establish mineral deficiencies and excesses over a two-seasonal grazing period (fall-winter and spring-summer corresponding to the rainy and dry seasons) according to variations of year, region and animal classes in Sabalan, Iran. In each flock, ten sheep (38-50 kg body weight, three females groups: yearlings, growing and mature, in addition to one male group)

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... re selected for the study purpose. Approximately 10 ml blood samples were collected in two stages by jugular vein, which were then centrifuged, and plasma or serum were obtained. Plasma phosphorous (P) was determined by the colorimetric method. Serum Ca and Mg were measured by atomic absorption spectrophotometry. Overall, means of serum Ca, Mg and plasma P concentrations were 11.73, 3.24 and 4.92 mg dl-1 in dry season and 12.01, 3.17 and 5.3 mg dl-1 in rainy season, respectively. Year, season and region significantly affected (P< 0.001) serum concentration of Ca but region had no effect (P> 0.05) on Plasma P. Unlike season, year effect on Mg concentration was significant (P< 0.05). These macro-mineral concentrations of serum and plasma were not different (P> 0.05) between animal classes. Ca and P deficiencies were higher in rainy than the dry season (6.24 vs. 3.38 and 16.52 vs. 15.2 percent, respectively). Although overall mean of serum Ca and P had higher values than the critical levels of these minerals in sheep blood, our results indicate that sheep in Sabalan need a common salt Ca and P supplement to enhance the blood level of these essential minerals in some sheep.