Effect of increasing equilibration time of diluted bull semen up to 72 h prior to freezing on sperm quality parameters and calving rate following artificial insemination

Abstract

An equilibration period of approximately 3-4 h prior to semen cryopreservation is standard practice for maintaining membrane integrity and motility of bull sperm. However, a number of studies indicate that an overnight equilibration period prior to freezing results in improved post-thaw semen quality thus optimising pregnancy rates. The aim of this study was to assess the effect of increasing the equilibration time of bull semen up to 72 h before freezing on sperm quality parameters and calving rate (CR) following artificial insemination (AI) with frozen-thawed semen. The effect of holding semen at 4 °C for 6, 24, 48 or 72 h post dilution before freezing on subsequent post-thaw total and progressive motility (Experiment 1) and field fertility (n = 1640 inseminations, Experiment 2) of frozen-thawed semen was assessed. Equilibration time did not affect post-thaw total and progressive motility (P > 0.05). In addition, there was no effect (P > 0.05) of equilibration time on field fertility with a CR of 53.3, 50.5, 51.3 and 47.3 for the 6, 24, 48 and 72 h treatments, respectively. In conclusion, increasing the equilibration time of diluted bull semen from 6 to 72 h had no significant effect on CR, within the expected range of fertility outcomes, thus providing semen processing centres with flexibility in the time which semen can be held prior to freezing.

Supplementation of Pandanus conoideus Oil in Cryopreservation Diluents for Maintaining the Semen Quality of Ongole Grade Bull

“…The method of equilibration in the refrigerator (5 o C) was already used in previous studies (Soltan et al, 2016;Elhammali et al, 2019). The durations of equilibration were 4 and 6 hours at 4 o C, according to Fleisch et al (2017) and Murphy et al (2017), respectively. Furthermore, the equilibrated semen was transferred into a Styrofoam box containing liquid nitrogen with a depth of about 10 cm above the surface of liquid nitrogen for 10 minutes, and then the semen was ready to be frozen into liquid nitrogen at -196 o C. The post-thawing evaluation was done by placing the straw into the warm water at 37 o C for 30 seconds with an observation time of 0 hours, 0.5 hours, and 1 hour.…”

Influence of seminal plasma during different stages of bovine sperm cryopreservation

“…Although the equilibrium step is considered an important period for interactions between environmental components (medium components) and sperm cells (Leite et al, 2010;Murphy et al, 2018;Watson, 1979), its length remains debatable. Leite et al (2010) and Fleisch et al (2017) reported that longer periods of equilibrium time provided greater preservation of sperm membranes.…”

“…After cooling, sperm are maintained between 6°C and 4°C for a period of time (named equilibrium phase). It is believed that the equilibrium time is important for adaptation of sperm membrane to low temperatures (Fleisch et al, 2017;Leite et al, 2010;Muiño et al, 2007), thereby allowing water translocation and reduction of injuries caused by ice nucleation (Murphy et al, 2018;Vishwanath & Shannon, 2000). During the freezing stage (below 0°C), sperm are exposed to the effects of ice crystal formation, hyperosmolarity (Hammerstedt et al, 1990), cellular dehydration (Grötter et al, 2019), and changes in cell volume and protein denaturation (Ugur et al, 2019).…”

Two melatonin treatments improve the conception rate after fixed‐time artificial insemination in beef heifers following synchronisation of oestrous cycles using the CoSynch‐56 protocol

“…Melatonin treatment has successfully been used to initiate ovarian cyclicity in anoestrous buffalo heifers 11 and increase plasma concentrations of GnRH and gonadotropins, promoting follicular growth and ovulation 12, 13 . The conception rate following AI is usually between 30% and 70% 14–22 . Early embryonic development may be negatively affected by insufficient progesterone (P4) production, with pregnancy failure attributed to insufficient luteal P4 production during early embryonic development 23 …”