Resumen de Effect of the primary cooling rate on the motility and fertility of frozen-thawed rabbit spermatozoa
Tatsuhiro Maeda, Enqi Liu, Kazutoshi Nishijima, Shinji Yamaguchi, Masatoshi Morimoto, Teruo Watanabe, Jianglin Fan, Shuji Kitajima
In the present study, we examined the effect of primary cooling rates on the motility and fertility of frozen-thawed rabbit spermatozoa. Rabbit semen diluted with an egg-yolk acetamide extender was cooled from room temperature to 5°C at four different rates (-0.1, -0.2, -0.4, -0.8°C/min) as a primary cooling step, then semen was frozen in liquid nitrogen vapour. After thawing, sperm cooled at -0.1°C/min showed the highest motility (40.7 ± 7.3%); there were no significant differences between the motilities of the -0.1, -0.2, and -0.4°C/min groups. The motility of frozen-thawed sperm cooled at -0.8°C/min (29.2 ± 6.8%) was significantly lower than that of sperm cooled at -0.1 and -0.2°C/min. The viability (-0.1°C/min, 38.1 ± 4.0%; -0.8°C/min, 24.3 ± 7.3%) of frozen-thawed sperm was closely related to its motility (-0.1°C/min, 36.7 ± 7.2%; -0.8°C/min, 22.3 ± 4.7%). Quality of post-thaw motile sperm cooled at different rates was estimated by comparing the fertilisation ability of the -0.1 and -0.8°C/min groups following artificial insemination. There were no significant differences in pregnancy rates and mean litter sizes. These data suggest that cooling rabbit semen at rates ranging from -0.1 to -0.8°C/min affects the viability but not the fertilisation capacity of motile spermatozoa after thawing.
