Influence of extenders and antioxidants on Nile tilapia (Oreochromis niloticus) sperm parameters

This study aimed to evaluate the effects of different dilutions of extenders (ionic, glucose, and bicine) and antioxidant concentrations on Nile tilapia sperm kinetics and membrane integrity parameters (MI). Antioxidants tested included taurine (1, 5, and 50 mmol), uric acid (0.5, 1, and 5 mmol), reduced glutathione (1, 5, and 10 mmol), and ascorbic acid (1, 10, and 50 mmol). Initially, ejaculates from five Nile tilapia were collected, evaluated, and diluted in a ratio of 1:3 into three aliquots, each with ionic, glucose, or bicine extenders. The samples were stored at 4 °C for 60 min and evaluated for kinetics and MI. The ionic extender showed higher MI and progressive motility. Then, ejaculates of four fish were collected to test each antioxidant. The samples were diluted in a ratio of 1:3, into a control group (without antioxidants) and the three concentrations in an ionic extender plus methanol 10 %. The samples were frozen/thawed and evaluated for kinetics and MI. Taurine at 1 mmol showed higher total motility, cells with medium velocity, and lower static cells. No differences were found in uric acid concentrations tested. Reduced glutathione treatments resulted in higher membrane damage, number of static cells, and lower total motility. Ascorbic acid addition decreased total motility and increased the number of static cells. Therefore, the addition of 1 mmol taurine was suitable for Nile tilapia sperm cryopreservation. Uric acid in tested concentrations maintained the sperm parameters, while reduced glutathione and ascorbic acid decreased sperm quality.