Effect of the primary cooling rate on the motility and fertility of frozen-thawed rabbit spermatozoa

Abstract

ABSTRACT: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 4 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.

Initial cooling time before freezing affects post‐thaw quality and reproductive performance of rabbit semen

“…were better than those obtained by other authors (Moc e, Lavara, & Vicente, 2010;Moc e et al, 2014;Viudes-de-Castro et al, 2014) who diluted the semen with freezing extender (containing CPA) at room temperature, that is, without a cooling phase, while results similar to ours were obtained by Moc e, Lavara, and Vicente (2003) and Maeda et al (2012).…”

Reducing the time rabbit sperm are held at 5 °C negatively affects their fertilizing ability after cryopreservation

“…Although rabbit sperm are considered to be cold shock resistant [3], it is likely that they suffer cold shock damage if cooled too quickly. Previous studies have shown that rabbit sperm cooled at À0.1 to À0.4 C/min resulted in higher in vitro sperm quality than a cooling rate of À0.8 C/min, although these different cooling rates did not result in different rabbit sperm fertilizing capacity [7].…”

“…Other recent studies evaluated the effects on how cooling rate [7] or equilibration time [8] affects rabbit sperm quality and fertilizing ability. However, in these studies the cooling, equilibration or both times were a minimum of 55 minutes.…”

Effect of different freezing velocities on the quality and fertilising ability of cryopreserved rabbit spermatozoa

“…For this reason, research has been conducted in the last few years with the objective of optimising the cryopreservation diluents and protocols for rabbit spermatozoa (Iaffaldano et al 2012;Maeda et al 2012;Maya-Soriano et al 2013;Rosato and Iaffaldano 2013) and understanding the parameters that could have an effect on rabbit sperm freezability (Lavara et al 2013). The damage that the spermatozoa accumulate during the cryopreservation protocol causes a decrease in the quality and in in vivo fertilising ability of the spermatozoa.…”