Factors Affecting Embryo Recovery Rate, Quality, and Diameter in Andalusian Donkey Jennies

Abstract

Embryo transfer and the vitrification of embryos could be used for the conservation and recovery of endangered donkey breeds. It is important to develop techniques that optimize recovery rates and the cryotolerance of donkey embryos. This study evaluates factors affecting the recovery rate, quality, and diameter of embryos obtained from donor jennies as a starting point for the use of vitrification and embryo transfer in the conservation of the Andalusian donkey. A total of 100 embryos were recovered out of 124 estrous cycles (80.6%). The donor jenny affected the rates of positive flushings (PFR; p = 0.040) and embryo recovery (ERR; p < 0.05) as well as embryo quality (p = 0.004). ERR was also affected by the number of flushings (p < 0.001), donor age (p < 0.05), successive cycle within donor (p < 0.001), and jacks (p < 0.05). Number of flushings (p < 0.001) and jack (p < 0.05) had a significant effect on PFR, whereas the day of flushing influenced the developmental stage (p < 0.001), embryo quality (p < 0.05), and diameter of embryos (p < 0.001). The number of flushings significantly influenced the diameter (p = 0.038) and embryo developmental stage (p = 0.001), whereas the developmental stage was statistically different between herds (p = 0.020). The factors influencing the success of this assisted reproductive technique were donor jenny, donor age, successive cycle within donor, day of flushing, number of flushings, and jack. The identification of these key points is crucial to achieve a higher efficiency of embryo transfer and vitrification processes, before considering their application in the conservation of endangered donkey breeds.

Hormonal Management for the Induction of Luteolysis and Ovulation in Andalusian Jennies: Effect on Reproductive Performance, Embryo Quality and Recovery Rate

“…The overall ERR obtained in this study (69.3%) was similar to that reported in the literature for donkeys (40.7–80.6%) [ 4 , 58 , 59 , 60 , 61 ]. Our results do not show any significant differences between PG treatments for PFR, ERR and EG, which is consistent with previous reports on mares [ 23 ].…”

“…Although the complete vial of Veterin Chorion contains 3000 IU of hCG, only 1500 IU was used for ovulation induction in this study. This dosage was previously described for jennies by Serres et al [ 68 ], and it was successfully used for inducing ovulation in jennies in later studies [ 61 , 69 , 70 , 71 , 72 ]. However, this is the first study in which this concentration of hCG is compared to 0.75 mg of deslorelin acetate for induction of ovulation in this species.…”

Colección, vitrificación y transferencia post-calentamiento de embriones equinos producidos in vivo: una revisión de literatura

“…Besides showing a high degree of variation, the data related to the per day embryo recovery rate in jennies are limited (Allen et al, 1985;Vendramini et al, 1997;Camillo et al, 2010;Peña-Alfaro et al, 2014;Bottrel et al, 2017;Pérez-Marín et al, 2017;Ottmann et al, 2018;Dorado et al, 2020). During the sixth PO day, the percentage of successful embryo collection ranges from forty-three (Vendramini et al, 1997) to seventy-five (Dorado et al, 2020). On the seventh PO day, it goes from twelve (Camillo et al, 2010) to eighty percent (Dorado et al, 2020).…”

“…During the sixth PO day, the percentage of successful embryo collection ranges from forty-three (Vendramini et al, 1997) to seventy-five (Dorado et al, 2020). On the seventh PO day, it goes from twelve (Camillo et al, 2010) to eighty percent (Dorado et al, 2020). Alternatively, if attempted from the eighth to the ninth PO day, the successful embryo collection rate is usually higher than fifty percent (Camillo et al, 2010;Peña-Alfaro et al, 2014;Dorado et al, 2020).…”

“…In general, the post-ovulation day selected to attempt an embryo recovery influences the percent of embryos collected. The successful recovery of equine embryos is influenced by multiple factors: age, number of cycles within each donor (Dorado et al, 2020), whether the semen used is either fresh, chilled, or frozen (Meadows et al, 2000), time of insemination relative to ovulation (Eldridge-Panuska et al, 2005), the season of the year; in mares, but not in jennies (Peréz-Marín et al, 2017;Dorado et al, 2020), number of ovulations per cycle; single or multiple (Squires et al, 1985), fertility of the horse or donkey (Peréz-Marín et al, 2017;Dorado et al, 2020) and other factors (Allen et al, 1985). In most cases the average rate of embryo recovery is higher than 50 percent; irrespective of whether its collection is attempted either on the sixth, seventh, eighth, or ninth PO days (Allen et al, 1985;Freeman et al, 1991;Hinrichs, 1990;Eldridge-Panuska et al, 2005).…”