Cryopreservation of channel catfish spermatozoa: Effect of cryoprotectant, straw size, and formulation of extender

Various aspects of the cryopreservation of spermatozoa of channel catfish (Ictalurus punctatus) were studied in relation to spermatozoa motility. The objectives were to evaluate 1) the efficacy of 5, 10 and 15% of methanal or n,n-dimethyl acetamide (DMA) as cryoprotectants; 2) the acute toxicity of 5, 10 and 15% methanal or DMA; 3) the use of 0.5-ml vs. 0.25-ml straws; 4) the efficacy of 5, 10 and 15% of methanal in Hanks' balanced salt solution (HBSS) or HBSS without glucose, and 5) the use of HBSS with or without 5% methanal. We found that use of 5% methanol as a cryoprotectant resulted in significantly higher post-thaw motility (P = 0.0001) than did 5, 10 or 15% DMA. The use of 5% of either cryoprotectant resulted in significantly higher post-thaw motility (P = 0.0001) than did 10 or 15% of the cryoprotectants. Samples containing 10 or 15% DMA had significantly lower motility (P = 0.0001) after 30 min exposure than did samples containing 5, 10 or 15% methanol. The use of 0.25-ml straws resulted in significantly higher post-thaw motility (P = 0.0001) than that of 0.5-ml straws. No difference was found in post-thaw motility between HBSS with and without glucose as the extenders. Cryopreservation in HBSS without addition of cryoprotectant resulted in post-thaw motility values of about 1%. (C) 1997 by Elsevier Science Inc.