Differences between first and second ejaculations regarding seminal plasma calcium, magnesium and total antioxidant capacity in dual-purpose Fleckvieh bulls and their relationships with semen quality.

Artificial insemination is a well-established and widely used method for genetic improvement in cattle breeding industry. Recently, researchers have shown an increased interest in the cryoprotective effects of minerals and antioxidants on semen. Previous studies on calcium (Ca) and magnesium (Mg), two main macro-minerals, have mainly investigated their roles in mammalian spermatogenesis and fertility. In addition, the experimental data examining the semen content regarding these minerals and antioxidants from different animal species are rather controversial and there is no general agreement about their associations with semen quality. Therefore, this study was conducted to assess the seminal plasma concentrations of Ca, Mg and total antioxidant capacity (TAC) in first and second ejaculations of dual-purpose Fleckvieh bulls and to link them to the sperm characteristics of fresh and frozen-thawed semen. Sperm progressive motility after thawing was used to classify the data into three groups: < 40.00%, 40.00 to 50.00% and > 50.00%. The measurements of two minerals and TAC were carried out using spectrophotometry and enzyme-linked immunosorbent assays, respectively. The results showed that there were significant differences in several parameters of semen quality between first and second ejaculations. No significant differences were also found on Ca and Mg concentrations and Ca/Mg ratio. The TAC level was significantly higher in the first ejaculation than the second one. The findings of this study suggest that TAC is a potential marker for bull semen quality assessment in the frozen semen production industry.