Does MnTBAP ameliorate DNA fragmentation and in vivo fertility of frozen-thawed Arabian stallion sperm?

Overproduction of reactive oxygen species during sperm freeze-thawing process leads to membrane lipid peroxidation, DNA damage, motility loss, and subsequent death. This oxidative stress can be alleviated by the addition of some antioxidants to semen extenders prior to freezing. This study was performed to evaluate the in vitro effectiveness of MnTBAP (a cell permeable antioxidant) on stallion sperm freezability and in vivo fertility rate. Twenty-one ejaculates were, collected with missouri model artificial vagina (n = 3 stallions, seven ejaculate each), and diluted (1:2 v/v) with phosphocaseinate base INRA extender, containing 0 (control), 100, 200 and 300 μM of MnTBAP and frozen using acontrolled-rate freezing system. The following parameters were determined: sperm motility, viability, membrane integrity, acrosome abnormalities, lipid peroxidation and DNA fragmentation. MnTBAP improved horse semen quality parameters in a dose-dependent manner. The100 μM concentration of MnTBAP did not show a significant difference in semen parameters compare with control group (p > 0.05). Accordingly, the extender supplemented with 200 μM resulted in higher sperm total and progressive motility (55.3 ± 4.28% and 33.2 ± 2.90%), viability (43.9 ± 2.14%), and membrane integrity (50.8 ± 2.14%), provided a greater protective effect in the percentage of total abnormalities compare to other groups (p < 0.05), and showed lower sperm with damaged DNA with lower MDA levels (p < 0.001). Higher concentrations (300 μM) not only did not improve the results but inversely affected sperm parameters. Twelve mares were used for fertility trial in the cross over study of 60 deep horn inseminations performed using control (9/30 pregnancy/mare) and 200 μM - MnTBAP (14/30 pregnancy/mere) groups frozen semen. The Average pregnancy rates were not significantly different between control and treated group (30% and 46.66%respectively) (p > 0.05). Under the conditions of this study, 200 μM - MnTBAP reduced the oxidative stress and protect the DNA fragmentation of Arabian stallion sperm during cryopreservation; but did not improved pregnancy rates.