Effect of Cooling Rate to 5°C, Straw Size and Farm on Fertilizing Ability of Cryopreserved Rabbit Sperm

Abstract

High fertility and prolificacy in rabbits are currently only achieved using fresh sperm. This study was conducted to determine if the cooling rate to 5 °C, the straw size and the farm where artificial inseminations are performed have an impact on the fertilizing ability of rabbit sperm cryopreserved with an extender containing dimethyl sulphoxide (DMSO; 1.75 m) and sucrose (0.05 m). Slow cooling to 5 °C improved neither fertility rate (58 vs 56% kindling rate for fast and slow cooling, respectively) nor prolificacy (6.5 vs 8.7 total born for slow and fast cooling, respectively; p < 0.05) compared to fast cooling rate to 5 °C. The straw size did not have an effect on either fertility or prolificacy (47 vs 57% kindling rate and 6.3 vs 6.8 total born for sperm loaded into 0.25 and 0.5 ml straws, respectively). In addition, similar results were obtained between farms (46-57% kindling rate and 4.9-6.7 total born), although this effect should be studied further. In conclusion, with this extender, slow cooling does not present a beneficial effect on sperm fertilizing ability and either 0.25 or 0.5 ml straws can be used to freeze the sperm, obtaining similar results after artificial insemination. In addition, similar results were obtained between farms when using cryopreserved sperm, and these results were lower than those obtained after artificial insemination with fresh semen. Therefore, new approaches are needed to improve the results obtained when cryopreserved sperms are used before this type of sperm can be used for commercial purposes.

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

“…When using this diluent and 0.5-mL straws, the medium freezing rate (À408C min À1 ) provided a better quality after thawing, similar to that obtained with the control protocol. The freezing rate obtained for the 0.5-mL straws using the freezing diluent and protocol described in this study (straws suspended 5 cm above the liquid nitrogen level) was recently published (Mocé et al 2010). According to those results, the straws are frozen at an approximate freezing rate of À548C min À1 , which is intermediate between the medium and the fast protocols of the programmable freezer.…”

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

“…Effect of equilibration time at 5 C on the in vitro quality parameters of cryopreserved rabbit sperm For this experiment, nine different pooled ejaculate samples were split into six aliquots. Each aliquot was diluted (1:1; v:v) with the freezing diluent (Tris-citric acidglucose with 3.5 M of DMSO and 0.1 M of sucrose [6]) at room temperature (22 C), packaged into 0.5 mL plastic straws (Minitüb Ibérica S.L., Tarragona, Spain), which were sealed with polyvinyl alcohol (IMV Technologies, L'Aigle, France), and each group of straws placed into a 5 C chamber. Straws were removed from the chamber at 0, 10, 15, 20, 30, and 45 minutes (control; [9]) and frozen in static nitrogen vapor (5 cm above the liquid nitrogen) for 10 minutes, after which they were plunged into liquid nitrogen for storage [9].…”

“…The ejaculates were collected using an artificial vagina and prepared as described by Mocé et al [6]. Eighty-nine percent of the ejaculates collected fulfilled the quality parameters and were used for the experiments.…”

“…Current protocol for cryopreserving rabbit sperm is packaging the sperm into straws and then placing the straws into a 5 C chamber for 45 minutes before freezing [5]. However, more recent research indicates that this incubation period can be reduced to less than 10 minutes [6].…”

Genetics of fresh and frozen-thawed semen traits and their relationship with growth rate in rabbits

“…When AI with frozen-thawed sperm was performed, the possible losses of fertility were compensated by increasing the number of spermatozoa in the insemination doses (Salomon and Maxwell, 2000). For instance, despite the reduction in the number of motile and non-reacted acrosome sperm, the protocol used in the present study reported successful fertility rates, as shown in previous studies Mocé et al, 2010).…”