Practical protocols for timed artificial insemination of jennies using cooled or frozen donkey semen

Abstract

Background: With the expansion of the donkey industry, timed artificial insemination (TAI) is becoming increasingly important in the reproductive management of jennies, however, TAI has not been widely investigated in donkeys.Objectives: To develop efficient TAI protocols for cooled or frozen semen in jennies, based around ovulation induction with a GnRH analogue.Study design: Experimental exploratory study. Methods and Results:In experiment 1, the effects of different GnRH analogue (deslorelin) doses, follicle diameter (FD) at induction, repeated use of a GnRH analogue, and the influence of season on induction efficiency, as well as distribution of ovulations over time after induction were investigated. Induction efficiency was sufficient with 2.2 mg deslorelin (≥90% ovulation within 48 hours of treatment). Ovulation rate between 24 and 48 hours was highest when the FD at treatment was 31-35 mm, as compared to 25-30 mm or 36-40 mm. Repeated use of deslorelin or treatment during different seasons had no effect on induction efficiency. About 70% of ovulations occurred between 32 and 48 hours, and highest incidence of ovulation was at 36-38 hours after induction. In experiment 2, TAI using cooled semen (1 × 10 9 motile sperm in a 10 mL volume) was performed once at 8 hours after induction (n = 59).Pregnancy rate after TAI with cooled semen was 49.2% (29/59). In experiment 3, jennies were inseminated twice with 10 (n = 23), 5 (n = 31), 3 (n = 32), 2 (n = 82) and 1 (n = 66) straws (more than 50 × 10 6 motile spermatozoa in each 0.5 mL straw) of frozen semen at 34 and 42 hours after induction. The pregnancy rates were 30.4%, 35.5%, 34.4%, 29.3% and 28.8%, respectively (P > 0.05). Main limitations:In the frozen semen trial, 22.5% (68/302) jennies were excluded after failure to ovulate during the appropriate time interval. In addition, there were no control groups for the AI trials. Conclusion:When FD reaches 31-35 mm, a donkey jenny can be inseminated once using cooled semen at 8 hours or twice using frozen semen at 34 and 42 hours after | 1219 YANG et Al.

Ability of donkey sperm to tolerate cooling: Effect of extender base and removal of seminal plasma on sperm parameters and fertility rates in mares

“…To date, there is no gold standard protocol for cooling donkey semen, and clinical experience suggests that donkey semen has poor fertility and cooling ability when extended in commercially available equine SM-or milk-protein-based extenders (2). Even though some authors propose that this poor cooling ability may be circumvented by centrifuging jack semen to remove seminal plasma or adding 2% egg yolk to SM extenders, research is limited in this aspect and published results vary according to protocols (5,7,(24)(25)(26)(27)(28).…”

“…Even though some studies have reported fertility rates of cooled donkey semen ranging from 21 to 76% using extenders with different bases, the average period of storage in the majority of studies has been short (e.g., 2–8 h) ( 24 – 26 ) or mares were inseminated several times in the same estrous cycle ( 13 , 63 ). Therefore, in our previous study with cooled donkey semen ( 14 ), the authors deliberately mimicked conditions in equine practice where semen is often shipped over long distances for 24–48 h ( 2 ).…”

Optimization of recovery and maturation methods for cumulus‐oocyte complexes in jennies

“…Several studies have provided improvements to OPU in equines through gonadotropin treatment for 36 h before aspirating, and the recovery rate increased to nearly 70% (Morris, 2018). Previous report from our laboratory showed that GnRHa was efficient in inducing ovulation in donkeys, with more than 90% of donkeys ovulating within 48 h (Yang et al, 2021). Our results showed that the recovery rate of donkey preovulatory follicles (≥35 mm) after 24 h of GnRHa treatment was 72.2%, which is similar to equines (Carnevale et al, 2005).…”

Clinical insights: Assisted reproductive techniques: More than a solution to subfertility?

“…In this latter context, ovulation induction with a GnRH analogue was also recently shown to improve pregnancy rates in a donkey AI programme, despite reducing the frequency with which follicle development was monitored. In jennies, administering a GnRH analogue when the pre‐ovulatory follicle reached 31–35 mm appeared to be the optimal basis for fixed‐time AI using either chilled semen (AI 8 hours after GnRH analogue administration) or low doses of frozen‐thawed semen (AI 34 and 42 hours after GnRH) 3 ; achieving pregnancy rates of ~30% per cycle with as few as 100 million motile frozen‐thawed spermatozoa was particularly noteworthy given that previous studies have struggled to achieve commercially acceptable pregnancy rates using frozen‐thawed donkey semen.…”