Effects of seasonal and physiological variations on the serum major and trace element levels in sheep

The aim of this study was to investigate the possible effects of the seasonal and physiological variations on the Cu, Zn, Mg, Fe, Se, Ca, K, Na, Cl, and P concentrations and their relationships with the estradiol and progesterone levels in Sakiz-Ivesi sheep. For this purpose, 34 healthy Sakiz-Ivesi crossbreed sheep were divided into two groups. The first group (n=22) was mated and the second group (n=12) was not mated. They were raised under pasture conditions and without any dietary supplementation. Their serum samples were collected four times a year at each season and under each physiologic condition. The periods are 1=early pregnancy (October), 2=late pregnancy (January), 3=lactation (April), and 4=dry season (July). The results of this study indicated that (1) Mg concentrations in serum vary with seasonal variations but not physiological variations, (2) Fe and K concentrations in serum vary only with physiological variations, (3) the Cu concentration changes not only pregnancy but also through some other hormonal changes not caused by pregnancy, (4) Ca, P, and Se concentrations could vary with both physiologic and seasonal variations, (5) Zn, Na, and Cl were almost identical for both groups and altered depending on neither season of the year nor the physiologic status, (6) both increased estradiol level and increased progesterone level can raise Cu levels in serum, and (7) increased serum Ca concentrations are related with increased estradiol and decreased P and Mg levels. These observations suggest that seasonal and physiologic variations and sexual cycle have to be taken into consideration for a correct interpretation of elements status. If sheep are maintained at pasture conditions, the nutritional requirements must be supplemented during certain periods. Otherwise, it is apparent that this will cause a decline in the total performance of sheep and, consequently, economic lost.