Effect of semen extenders on the motility and viability of stored African Catfish (Clarias gariepinus) spermatozoa

This study assessed the effects of common extenders and diluents on the spermatozoa of African catfish (Clarias gariepinus), with the intent of obtaining a semen preservation protocol that can serve as a means of making fingerlings available to fish farmers all year round. Semen samples (milt) were pooled from mature broodstock males and pre-extension qualities were evaluated. Egg yolk, tomato juice and sodium citrate buffers were combined in four different trials and used to preserve obtained semen at temperatures of 5°C and -40°C for 8 days and 4 weeks respectively in different trials. Motility indices of extended, preserved, refrigerated and frozen semen were used to analyze the effect of the various combinations. Forward, progressive and rectilinear motion was employed as a significant measurement of the livability of extended sperm cells and the efficacy of the extender solution. The result of the study showed that the buffer (sodium citrate) on its own performed excellently well (sperm motility was 85%) in enhancing survival within the first 24-48 hours post extension; Semen extended with 20% tomato juice gave the best survival rate when stored at 5°C, because the sperm cells were still viable by day 6 postextension. Extender containing 20% egg yolk gave 70% motility while that containing 10% egg yolk mixed with 10% tomato juice gave 60% motility. However, motility decreased progressively as the period of storage increased. The results of the effect of freezing (at -40°C) on motility revealed that no motility was observed in all the cryopreserved trials except the sample containing 10% egg yolk and 10% tomato juice, which recorded 10% post-thaw motility.