One of the most significant indicators affecting male fertility is the sperm nuclear and mitochondrial DNA fragmentation index (DFI). DNA damage depends on biotic and abiotic factors, leading to oxidative stress (O.S.). This research aimed to investigate the relationship between mitochondrial dysfunction of spermatozoa and their biological adequacy. The research material was frozen-thawed sperm samples from the Ayrshire, Russian Black Pied Holstein, Russian Red Pied Holstein, Limousin, and Polled Russian breeding bulls. Assessments of mobility, morphology, and fragmentation index were performed using computer-assisted sperm analysis (CASA). It was found that there is a negative correlation between sperm activity and mitochondrial dysfunction with the correlation coefficient r = -0.24. The incidence of abnormal spermatozoa correlated with sperm dysfunction r = 0.77. The nDNA fragmentation index in chromatin varied from 0 to 25%
