Effects of using ethylene glycol with lecithin in the presence or absence of sugar on the post-thaw motility and morphology of rapidly frozen bovine spermatozoa

In this study, the semen was collected from a 3 year old Gyr (37.5) x Holstein Freesian (62.5%) bull using the artificial vagina method. Evaluation of the volume, consistency, motility and dilution of the fresh semen and packaging of the extended semen were for the control and treatment groups. For the control, the straws were equilibrated for 4 hours at 5 deg C. Following equilibrium, two samples were obtained and the motility and morphology were evaluated. Afterwards, gradual freezing was done in liquid nitrogen. After an hour, semen was thawed in 35 deg C for 18-20 seconds. The post-thaw motility and morphology were evaluated. For the treatment groups, the straws were equilibrated at 20 deg C for 10 minutes and then divided into 3 sets and then equilibrated for 15, 30, 60 minutes at 5 deg C. After which they were suspended in liquid nitrogen vapor (-170 deg C) for 2 minutes before it was plunged in liquid nitrogen (-196 deg C). The frozen semen was thawed at 35 deg C for 18-20 seconds and the motility and morphology was examined. The smears of the sample were stained with Giemsa. Percentages of abnormalities were determined by counting 100 sperm cells. This study demonstrated that the integration of cryoprotectant did not satisfy the required viscosity required of the cryopreservation solution for the survival of bovine spermatozoa. The effect was observed through the decrease in the motility and increase in sperm abnormalities during extension and after thawing of frozen bovine spermatozoa. The absence of sugar resulted to a decrease in the viscosity of the solution resulting to a drop of post-thaw motility when subjected to different equilibrium times. It was also observed that even if sugar is added, a drop in motility after thawing was also observed. The combination of lecithin, ethylene glycol and sugar did not protect the semen during cryopreservation. Incorporation of 1.5 grams of lecithin was insufficient to increase the viscosity of the solution. High incidence of tertiary abnormalities was observed from treatment 1, 2, 3 and 4 compared to the control. Macromolecules like lecithin and sugar increase the viscosity of the freezing solution, thus, increasing the possibility of vitrifications and protecting the spermatozoa from cryopreservation. However, this was not observed in this study. The above findings showed that the combination of ethylene glycol during extension and lecithin in the presence or absence of sugar did not sufficiently satisfy the requirement of freezing solutions. Further studies should be conducted to determine the proper lecithin concentration that would sufficiently protect bull spermatozoa during cryopreservation.