Abstract
Background:
Efficient detection of the optimal mating moment is essential for improving the reproductive performance of mares. Traditional methods mainly rely on ultrasonography and hormonal monitoring, but behavioral cues remain widely used in field conditions. Among these, the intensities of the straddle stance and urination are commonly observed, however, their physiological relevance and predictive value for successful mating remain insufficiently documented.

Aim:
This study aimed to evaluate whether the intensities of the straddle stance and urination can serve as reliable behavioral indicators of follicular maturity, estrous day, and pregnancy rate.

Methods:
The experiment involved 126 Arabian mares that were monitored throughout the breeding season during the cyclic and foaling estrus. The intensity of both straddle stance and urination were scored on a three-point scale (from + to +++). The estrous mares’ follicular activity was monitored using ultrasonography. Estrus day and pregnancy rates were recorded.

Results:
Younger mares displayed a high rate of ovarian resumption in March and April of the breeding season, and older mares reached the highest rates in February and March. Mares with an intense straddle stance (+++) had the largest follicles (p < 0.01). However, mares showed intense urination (+++) at later estrus days (p < 0.01). The highest pregnancy rates at 14 and 35 days post-mating (42.9%) were recorded in foaling estrus mares showing intense urination without embryonic resorption. Cyclic estrus mares showing weak straddle stance (+) had the highest pregnancy rates (56.3%) followed by 6.3% embryonic resorption.

Conclusion:
These findings indicate that straddle stance intensity reflects optimal follicular size, whereas urination intensity shows a context-dependent association with estrus day and pregnancy rate, particularly in foaling mares. Integrating the intensity of these behavioral indicators with routine reproductive assessments may improve mating decision accuracy and enhance reproductive outcomes in mares.

Key words: Follicle size; Intensity; Pregnancy rate; Straddle stance; Urination.