Sperm function and oxidative status: Effect on fertility in Bos taurus and Bos indicus bulls when semen is used for fixed-time artificial insemination.

Semen quality is one of the criteria used for the selection of bulls with relatively greater fertility. In addition, bull fertility depends on the integrity and function of all sperm structures. The aim of this study, therefore, was to determine associations when there was conducting of conventional and functional techniques for the evaluation of sperm samples from bulls with known fertility history as determined when semen from these bulls was used for fixed-time artificial insemination programs. The study was designed in a 2 × 2 factorial arrangement, with one factor being breed (Angus x Nellore) and the other fertility (greater x lesser). Greater fertility groups were composed of ten Angus and 11 Nellore bulls, while lesser fertility groups were composed of ten Angus and seven Nellore bulls. Sperm were analyzed, in four cryopreserved distinct batches for each animal, for morphology, kinetics, plasma and acrosomal membrane integrity, mitochondrial activity and mitochondrial membrane potential, DNA integrity and oxidative status. There was no difference in characteristics commonly used in sperm quality conventional analysis. The results from functional analysis indicated an important association between mitochondrial dysfunctions, oxidative stress, and damage to sperm structures in lesser fertility bulls. Greater fertility bulls had greater sperm quality and indicators of functional cell structures. The associations, when there were evaluations using different techniques, indicate the importance of evaluation and correlation between different sperm functions to understand effects of distinct parameters on sperm fertilization capacity.