Differences between some biochemical components in seminal plasma of first and second ejaculations in dual-purpose Simmental () bulls and their relationships with semen quality parameters.

This study aimed to evaluate differences in seminal plasma zinc (Zn), copper (Cu), iron (Fe), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) levels in the first and second ejaculations and their relationships with semen quality parameters in bulls. Repetitive ejaculates were separately collected, analyzed, and frozen from the sires. Progressive motility of frozen-thawed semen (PMFT) was considered the main factor for more data classification into three following groups: <40.00%, 40.00 - 50.00%, and >50.00%. Seminal plasma trace elements and enzymes were determined using atomic absorption spectrometry and ELISA, respectively. The results revealed significant differences between the first and second ejaculations. Semen concentration, SOD, GPx, and Fe were different in ejaculations. Although PMFT groups in different ejaculations did not show significant differences, there was significant alteration between different PMFT groups and first and second ejaculations. All frozen-thawed semen CASA parameters (except lateral head displacement) were associated with fresh motility parameters and before and after thawing sperm viability. Also, a correlation between seminal Zn concentration with fresh semen gross and progressive motility, average path velocity, and beat cross frequency, Cu with SOD and Fe and semen concentration was observed. CAT was associated with fresh and frozen-thawed sperm motility parameters except for lateral head displacement and angular displacement. Although our findings showed differences between the first and second ejaculations in some parameters, PMFT, which is the most important indicator for estimating bull fertility, was not different between them.