Comparison of two different antioxidants in a nano lecithin-based extender for bull sperm cryopreservation

The objective of the present study was to assess the effect of two different antioxidants, enzymatic compared with non-enzymatic, in a nano lecithin-based extender on post-thaw bull sperm quality. Semen samples (n = 36) were collected from six bulls. In the first experiment, 11 different extenders were prepared by adding five quantities of vitamin E (α-tocopherol) as a non-enzymatic antioxidant (VE: 0.1, 0.2, 0.4, 0.6 and 1.0 mM), or four quantities of glutathione peroxidase (GPx) as an enzymatic antioxidant (GPx: 0.5, 1, 2 and 3 mM) to the extender. Other extenders were a Control 1 (C1: Extender with ethanol) and Control 2 (C2: Extender without ethanol). Sperm motility (CASA), plasma membrane functionality test (HOST) and lipid peroxidation (MDA) were assessed to determine the optimal treatment in the first experiment. In the second experiment, the optimally supplemented group from the first experiment (GPx-1) was compared to C2 group. Apoptotic-like changes (Annexin staining), mitochondrial activity (Rhodamine-123 staining), acrosome integrity (PSA staining), DNA fragmentation (SCSA test) and in vitro embryo production capacity were evaluated. In the first experiment, there were the greatest percentages of plasma membrane functionality and least MDA (P ≤ 0.05) in sperm diluted GPx-1 group. In the second experiment, percentage of live sperm, blastocyst formation and hatching rate were greater (P ≤ 0.05) in the GPx-1 group compared with C2 group. In conclusion, data indicate adding 1.0 mM GPx as an enzymatic antioxidant to the nano lecithin-based extender can improve post-thaw quality and in vitro fertility of bull sperm.