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

• Published in: Theriogenology 2018-03, Vol.108, p.217-222
• Main Authors: Murphy, E.M., Eivers, B., O'Meara, C.M., Lonergan, P., Fair, S.
• Format: Article
• Language: English
• Subjects: Bovine; Fertility; Frozen-thawed semen; Sperm
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/j.theriogenology.2017.11.034

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. •Increasing equilibration time prior to freezing from 6 to 72 h had no significant in vitro effect on bull sperm quality.•Equilibrating bull sperm for 24 h prior to freezing resulted in the highest post-thaw total and progressive motility scores.•Increasing the equilibration time up to 72 h did not significantly affect calving rate.