Effect of Different Extenders and Storage Periods on Motility and Fertilization Success of Grass Carp (Ctenopharyngodon idella) Sperm During Spawning Season

The present study was conducted to evaluate the effect of different extenders and storage periods on motility and fertilizing ability of short-term stored grass carp sperm during spawning season. Sperm was collected from anesthesized males by the abdominal massage method. Having determined the main spermatological properties, the pooled ejaculates were diluted with 3 different extenders at a ratio of 1:3. The diluted sperm was packaged in small tubes and following, the tubes were stored at 4°C in a refrigerator for 8 hours. During preservation motility (%), motility duration (s) and fertilization (%) capacity of stored sperm were evaluated 2 hours intervals. Fertilization was carried out using the dry fertilization technique at 2x10 spermatozoa/egg dosage. The fertilization success was determined as the percent of eyed eggs 3-4 days after fertilization. At the end of 8 hours of storage, the highest sperm motility was found as 35±2.89% (P<0.05) with extender II in June whereas the highest motility duration was determined (56±6.35 s) (P<0.05) with extender I in May. Also, the highest fertilization rate was determined as 25±1.15% (P<0.05) with extender I in June. In conclusion, results of the present study indicated that composition of extenders, spermatozoa/egg ratio and stage of the spawning season is important to improve fertilizing ability of cold stored grass carp sperm.