Correlação da integridade cromatínica e da morfometria da cabeça dos espermatozoides com a produção in vitro de embriões e taxa de prenhez na raça Senepol

Abstract

This study assessed chromatin integrity and sperm head morphometry in Senepol bull semen to elucidate the relationships between these parameters and in vitro embryo production (IVEP) outcomes—specifically cleavage, embryonic development, and blastocyst rates—as well as pregnancy rates in recipient cows following embryo transfer. Cryopreserved semen samples, previously utilized in a commercial IVEP laboratory, were processed into smears and stained using Toluidine Blue or the Feulgen reaction for digital imaging. Additionally, the Sperm Chromatin Structure Assay (SCSA) was performed to determine the percentage of cells with DNA fragmentation. Computational image analysis of the stained smears quantified various sperm head characteristics, including average decompaction and heterogeneity of sperm chromatin, percentage of spermatozoa with chromatin decompaction in specific regions of the sperm head, and diverse morphometric parameters. The findings revealed a moderate negative correlation between DNA fragmentation (SCSA) and cleavage rates. Similarly, total chromatin decompaction identified via the Feulgen reaction correlated negatively with blastocyst rates. Morphometric analysis demonstrated that ellipticity was significantly and positively correlated with pregnancy rates, whereas the width-to-length ratio and form factor exhibited negative correlations with the same outcome. These data demonstrate that even in semen samples deemed fertile by conventional andrological standards, chromatin alterations can compromise IVEP efficiency and subsequent pregnancy rates. While both SCSA and computational analysis of Feulgen-stained smears show moderate efficacy in detecting such alterations, reduced sperm head ellipticity resulting from chromatin decompaction— even when undetected by direct chromatin assays—serves as a robust predictor of IVEP performance and post-transfer pregnancy success.