Effect of freezing techniques, extenders and cryoprotectants on the fertilization rate of frozen rainbow trout (Oncorhynchus mykiss) sperm

Abstract

Rainbow trout (Oncorhynchus mykiss) sperm was frozen in liquid nitrogen in straws or as pellets on dry ice and stored in liquid nitrogen until artificial insemination. Sperm was diluted with one of three extenders containing 15% DMSO or 15% DMA as a cryoprotectant at a ratio of one part sperm to two parts extender. The straws were thawed in a water bath while the frozen pellets were thawed in their own extenders at 30oC for 30 s. For both freezing methods, the best fertil- ization results were obtained with extender III containing 15% DMSO, 52.3% (56.3% of the con- trol) for sperm frozen in straws and 48.4% (52.4% of the control) for sperm frozen as pellets. The interaction between extender and cryoprotectant was statistically significant (p<0.05).