Objectives: 

Various investigations including women, sheep and laboratory animals have shown increased erythrocytemia around the time of ovulation (Harewood et al., 1996; Krajnicáková et al., 1995; Dapper and Didia, 2002). This increase of hematocrit (HTO) has been related to functional and morphological transformations of the reproductive system as well as the influence of estrogen during estrus. However, the increase of plasma volume during the luteal phase significantly decreases HTO related to the combined effect of oestradiol-17β (E2) and progesterone (Chapman et al., 1997). Based on these original ideas, the aim of this study was to determine if the dynamics of E2 could be related to the response in erythrocytemia in Spanish Purebred mares during ovulatory period.

Materials: 

A total of 25 Spanish Purebred mares aged between 5 and 15 years were analyzed. The control of follicular development was performed by ultrasonography (Sonosite 180 Plus). When preovulatory follicle was detected (40.23 ± 1.37 mm), venous blood samples were extracted for determination of HTO and E2. HTO was analyzed by microhematocrit technique using a microcentrifuge (Quims, Q222H) and serum concentrations of E2 by competitive immunoenzymatic techniques.

Results: 

HTO values and E2 concentrations showed a significant increase to the day of ovulation, with mean values of 34.19 ± 4.70% and 37.59 ± 0.80 pg/ml, respectively, with a correlation coefficient of r = 0.09 between both parameters.

Conclusions: 

In conclusion, the dynamics of E2 dismisses any influence of estrogen on the erythrocyte parameters in Spanish Purebed mares, despite the similarity in the evolution of both parameters. Indeed, should be considered non-hormonal factors in the interpretation of the erythrocyte parameters in cyclic mares at the time of ovulation.