Teratozoospermia in tropical stallions: integrating morphology, heat stress and molecular alterations

Abstract

The fertility of stallions in tropical regions is strongly influenced by semen quality, with sperm morphology being one of the main indicators of reproductive performance. Structural alterations, grouped under the term teratozoospermia, compromise fertilizing capacity and are associated with subfertility. This study aimed to conduct an integrative literature review on teratozoospermia in stallions under tropical climate conditions, gathering morphological, methodological, environmental, and molecular evidence. Studies analyzed addressed racial variations in sperm morphology, staining and evaluation methodologies, the impact of thermal stress on seminal parameters and testicular hemodynamics, as well as comparisons with human models and proteomic analyses. Results showed that different breeds present distinct proportions of normal sperm and specific defects; that methodological variability can generate divergences of up to 15% in the identification of abnormalities; and that thermal stress in tropical climates reduces motility, increases defects and DNA fragmentation, compromising fertility. Comparative evidence in humans reinforces the universality of thermal damage mechanisms, while proteomic analyses reveal alterations in acrosomal enzymes and structural proteins, broadening the understanding of subfertility.It is concluded that teratozoospermia in tropical stallions is a multifactorial phenomenon, resulting from the interaction between racial predispositions, methodological variability, environmental stress, and molecular alterations. The integration of morphological analyses, thermal comfort indices, and proteomic approaches represents a promising strategy for reproductive diagnosis and management adapted to tropical conditions.