Macro-elements compositions in ovarian follicular fluid of mares in relation of season and follicles size

The aim of the study was to determine the concentration of macro-elements in the fluid follicles of different sizes in season and out of breeding season in mares. Ovaries were obtained after the slaughter of the summer (N = 98) and winter (N = 77). In the obtained follicular fluid the concentration of magnesium (Mg), calcium, total (Ca) and phosphorus (P) was determined. In the summer, the concentrations of Mg and Ca were lower than in winter (P < 0.01). In the summer, the concentration of Mg was higher in small follicles and the concentration of Ca was lower in larger follicles (P < 0.05). The concentration of P in the follicular fluid during the summer and winter seasons was not statistically different. However, the seasonal differences in the concentration of P were between the small follicles. In this group of follicles the concentration of P in the summer was significantly higher than in the winter (P < 0.01). Moreover, the concentration of P was significantly different depending on the size of the follicles in the summer During this period, the concentration of P in small follicles was higher than in the larger follicles (P < 0.01). In the summer, a negative correlation was between the concentration of Ca and Mg (r = -0.29, P < 0.05) and between the concentration of Ca and P (r = -0.46, P < 0.01). In winter, there was no correlation between the analyzed elements. The recorded differences in the concentration of follicular magnesium, calcium and phosphorus indicate that the ionic composition of follicular fluid in horses may depend on the size of the follicles, and on the seasonal changes in the activity of the ovaries.