THERMAL COMFORT AND SEMINAL TRAITS IN STALLION REPRODUCTION: NEW METHODS TO UNDERSTAND THESE RELATIONSHIPS

Stallion breeding is mostly based on desirable phenotypic traits, with little consideration for semen quality. This study aimed to identify the relationships between different semen parameters in equine reproduction, using non-invasive methods, during summer and winter, using an integrative approach. Twenty-four stallions were evaluated, in which semen collections, testicular thermography, and Doppler velocimetry of the testicular artery by Doppler ultrasonography were performed, in addition to the measurement of physiological, environmental, and heat stress parameters, both in winter and summer. Statistical tests included univariate and multivariate analyses in SPSS® software (SPSS, 2012). Sperm defects, environmental temperature, and heat stress indices were higher in summer than in winter. In contrast, systolic and diastolic velocities, sperm motility, and vigor were higher in winter, which was attributed to the increase in environmental temperature and mean testicular temperature in summer. Environmental and thermal comfort variables showed significant correlations with seminal parameters in summer. In winter, there was a significant correlation between Doppler-measured variables, motility, vigor, and testicular temperature assessed by thermography. The analyzed indices characterized the thermal, circulatory, and seminal parameters of stallions, evidencing their differences and correlations between the seasons of the year, providing relevant data for the introduction of Doppler ultrasonography and infrared thermography in the evaluations of stallion fertility, thermal comfort, and choice of the ideal season for reproduction.

Hypothesis: Exposure to high environmental temperatures, especially in summer, is expected to negatively influence the sperm quality of stallions. Non-invasive methods, such as thermography and Doppler ultrasonography, can effectively detect these changes, contributing to adequate reproductive management.

马种繁殖主要基于理想的表型特征，而对精液质量关注甚少。本研究旨在利用非侵入性方法，在夏季和冬季通过整合性方法，探讨马匹繁殖中不同精液参数之间的关系。对二十四匹种马进行了评估，包括精液采集、睾丸热成像以及通过多普勒超声进行睾丸动脉的多普勒速度测量，此外还测量了生理、环境和热应激参数，包括冬季和夏季的数据。统计测试包括SPSS®软件（SPSS，2012）中的单变量和多变量分析。夏季精子缺陷、环境温度和热应激指数高于冬季。相反，冬季的收缩和舒张速度、精子活力以及精子活力均高于夏季，这归因于夏季环境温度和平均睾丸温度的升高。在夏季，环境和热舒适变量与精液参数之间存在显著相关性。在冬季，多普勒测量的变量、活力、活力和通过热成像评估的睾丸温度之间存在显著相关性。分析指数描绘了种马的温度、循环和精液参数，证实了年度季节之间的差异和相关性，为引入多普勒超声和红外热成像评估种马繁殖力、热舒适度和选择最佳繁殖季节提供了相关数据。

假设：暴露于高环境温度，尤其是在夏季，预计会对种马的精子质量产生负面影响。如热成像和多普勒超声等非侵入性方法可以有效地检测这些变化，有助于合理的繁殖管理。