First pregnancies in jennies with vitrified donkey semen using a new warming method

Sperm vitrification in horses and donkeys

Sperm vitrification is an alternative freezing method, which includes high cooling rates and non-permeable cryoprotectants agents. The first attempt in equids was using the spheres technique by directly dropping small volumes of the sperm into liquid nitrogen. Later, vitrification was developed using 0.25 mL straws with outer covers, which resulted in similar progressive motility when compared to conventional freezing in donkeys (44.3 ± 15.0 % vs. 44.7 ± 18.2 %) or even higher in horses (48.2 ± 2.3 % vs. 37.3 ± 2.2 %). Subsequently, the vitrification of larger volumes of sperm in 0.5 mL straws was evaluated, but the results showed poor sperm quality after different warming procedures. Finally, fertility was assessed in vitro and in vivo. In horses, the sperm fertilizing capacity was assessed utilizing heterologous in vitro fertilization (IVF) and vitrified sperm showed the ability to penetrate cattle oocytes, leading to pronuclear formation and hybrid embryo cleavage. In donkeys, fertility trials were conducted in vivo on a small group of jennies, showing no statistically significant difference in pregnancy rates between artificial insemination (AI) with vitrified semen (22%) or frozen semen (10%); however, the uterine inflammatory response after AI with vitrified semen solved faster than frozen semen. In conclusion, sperm vitrification has been optimized in horses and donkeys using 0.25 mL straws with outer covers and can be considered as an alternative to conventional freezing.

Is platelet-rich plasma effective in treating uterine inflammation in jennies inseminated with cryopreserved donkey semen?

Despite frozen donkey semen demonstrating high quality after thawing and achieving suitable pregnancy rates in mares, it yields unsatisfactory results in jennies, likely due to a stronger uterine inflammatory response. This study assessed the effects of platelet-rich plasma (PRP) on uterine inflammation and pregnancy rates in jennies inseminated with frozen donkey semen. Estrous cycles from 11 jennies were assigned to three groups: Control (CTR, n = 22) with no treatment; Single PRP infusion (S-PRP, n = 22) administered 30 h after ovulation induction, prior to artificial insemination (AI); and Double PRP infusion (D-PRP, n = 21) with the first infusion at 30 h after ovulation induction and the second 4 h after AI. Insemination was performed with frozen donkey semen (1 billion sperm) deposited deeply in the uterine horn immediately after ovulation. Endometrial edema, intrauterine fluid (IUF), uterine vascularization, and endometrial cytology were evaluated pre-AI (TCt) and post-AI (6, 24, and 48 h). Uterine biopsies were taken at T48 for histopathological and collagen evaluation. Peripheral blood samples were collected on D5 for serum progesterone measurement, and pregnancy was evaluated via ultrasonography on D14. Data were analyzed using GLMMs, ANOVA, Friedman, and Kruskal-Wallis tests in SAS and GraphPad Prism, with significance set at p < 0.05. The S-PRP group showed less IUF accumulation than the CTR group at T6. Other parameters showed no significant differences among the groups. Cytology revealed a high percentage of inflammatory cells at T6 in all groups, which decreased in subsequent evaluations. In the CTR group, neutrophil percentages were similar to TCt at T24, while treated groups reached this similarity only by T48. Eosinophil percentages increased over time only in the treated groups. Pregnancy rates showed no differences among the groups (CTR: 0 %, S-PRP: 0 %, D-PRP: 10 %). Results indicate that PRP treatments were ineffective in modulating uterine inflammation and did not enhance pregnancy rates in jennies inseminated with frozen donkey semen.

Ultrasonographic Assessment of Testicular Biometry and Arterial Blood Flow in Pre- and Postpubertal Miranda Donkeys: Correlations With Semen Quality Parameters

The main goals of this study were to document and compare the normal ranges of testicular haemodynamic parameters in pre- (aged 8-12 months; n = 4) and postpubertal (aged 24-259 months; n = 16) Miranda donkeys in the breeding season, and to correlate animal biometric data and testicular Doppler indices with basic semen quality parameters of sexually mature jacks. Colour and pulsed-Doppler ultrasonography were employed to assess blood flow in the left and right distal supratesticular artery (DsTA) and their marginal branches (marginal arteries-MA). Peak systolic velocity (PSV), end diastolic velocity (EDV), pulsatility index (PI) and resistive index (RI) were evaluated in both blood vessels, and TAMV (time-averaged mean velocity), TABF (total arterial blood flow) and TABF rate (TABF-R) were calculated for MA. The mean diameter of MA was greater (p < 0.05; 0.24 ± 0.05 vs. 0.19 ± 0.05 cm; mean ± SD) but TABF-R was less (p < 0.05; 0.004 ± 0.004 vs. 0.02 ± 0.01 mL/s/cm3) in sexually mature donkeys compared with prepubertal animals. Apart from RI values for the right testicle of prepubertal donkeys, PI and RI were consistently greater (p < 0.05) in DsTA compared with MA. Significant correlations were found among select biometric and haemodynamic attributes of the testes (height, width and length, TV, TTV and PSV-ST) and ejaculate characteristics (volume, sperm defects-total, head and midpiece) in sexually mature donkeys (n = 8). The present results highlight the importance of scrotal ultrasonography for the reproductive assessment of jacks and provide reference values, based on the available subpopulation of Miranda donkeys that can be used in their clinical and reproductive management and research, or conservation programmes.

The ability of donkey sperm to induce oocyte activation and mule embryo development after ICSI

Members of the Equus genus exhibit a fascinating capacity for hybridization, giving rise to healthy offspring. Mules, resulting from the mating of a mare with a jack, represent the most prevalent equid hybrid, serving diverse roles in our society. While in vitro embryo production, particularly through Intracytoplasmic Sperm Injection (ICSI), has rapidly gained significance in domestic horses, the in vitro production in other equids remains largely unexplored. Utilizing donkey sperm for fertilizing horse oocytes not only addresses this gap but also provides an opportunity to investigate donkey sperm's fertilization capability in vitro to further improve donkey ICSI. In this work, we initially studied the localization of donkey sperm Phospholipase C zeta (PLCζ) and assessed the sperm's capacity to induce pronuclear formation and maternal SMARCA4 recruitment upon injection into pig oocytes through ICSI. Subsequently, we investigated the injection of donkey sperm into horse oocytes, evaluating in vitro production up to the blastocyst stage using sperm from different jacks, including frozen and refrigerated samples. Distinct patterns of PLCζ localization were observed for donkey sperm cells compared to their horse counterparts. Additionally, donkey sperm exhibits a reduced ability to induce porcine oocyte activation. However, when injected into horse oocytes, donkey sperm demonstrated sufficient capability to induce oocyte activation as no discernible differences in cleavage or blastocyst rates are observed between in vitro produced mules and horse ICSI embryos. Our study not only delineates PLCζ localization in donkey sperm but also suggests potential differences in the ability to induce oocyte activation in pigs compared to horses while observing no distinctions in pronuclear recruitment of SMARCA4. Interestingly, donkey sperm remains sufficiently capable of inducing horse oocyte activation for in vitro mule blastocyst production.

Donkey semen cryopreservation: Alternatives with permeable, non-permeable cryoprotectants and seminal plasma

Cryopreservation of semen is an important technique to preserve genetic material. Yet, pregnancy rates in jennies after artificial insemination with frozen-thawed donkey semen are poor. This condition has been attributed to the impact of permeable cryoprotectants, that could cause high post-breeding endometritis. Removal of seminal plasma (SP) prior to semen freezing process is another contributing factor. SP is involved in a multitude of sperm functions and events preceding fertilization and has a mediating effect of sperm capacitation and postcoital uterine inflammatory response. The aim of this study was to evaluate different alternatives in donkey semen cryopreservation with permeable, non-permeable cryoprotectants, BSA and SP. Thirty ejaculates from 10 donkeys were cryopreserved with different combinations of dimethylformamide (DMF, 5%), sucrose (SUC, 200 mM) and homologous SP (10%): DMF (T1), DMF/SP (T2), SUC/BSA (T3), SUC/BSA/SP (T4), DMF/SUC/BSA (T5), DMF/SUC/BSA/SP (T6), DMF/BSA (T7) and DMF/BSA/SP (T8). After thawing, sperm motility and kinetics were assessed by computerized semen analysis. Sperm vitality (SV) was evaluated by fluorescence microscopy, functional membrane integrity (FMI) by the HOST test, abnormal morphology by eosin-nigrosin staining and sperm membrane stability by flow cytometry. For statistical analysis, sperm quality indexes (SQi) were obtained, general linear models were carried out and mean comparisons were made by the Tukey test. T1, T2, T5, T6, and T7 had higher and equivalent results for motility, most kinetic parameters and function membrane integrity. Cryopreservation of donkey semen without permeable cryoprotectant (T3 and T4) showed a reduction in motility, kinetics, SV, FMI and SQi. T5 showed a reduction in progressive motility, sperm velocities, IMF and SQi compared to other DMF treatments. T6 and T8 achieved higher SQi values compared to T1, but they were not different compared to T2 and T7. T1 had a smaller sperm population with low-M540 compared to T3. It is concluded that the use of permeable cryoprotectant is essential to achieve higher post-thaw quality of donkey semen. In addition, the combined use of BSA, SUC and/or PS may provide additional sperm protection compared to the individual use of DMF.

Vitrification of Iberian wolf (Canis lupus signatus) sperm: A possible alternative to conventional cryopreservation

Sperm vitrification is a simple, inexpensive method that allows the cryopreservation of sperm in the field and for endangered species is a useful alternative to conventional freezing. The study, therefore, is focused on the suitability of vitrification for cryopreserving Iberian wolf sperm and utilizing plasma testosterone concentration as a marker for procedure efficacy. Sperm and blood samples were collected from 17 wolves. There were 14 samples suitable for cryopreservation (12 ejaculated and two epididymal). Immediately after collection, these samples were proportioned into two aliquots for conventional freezing using a Tris-citric acid-glucose based extender (TCG) or vitrification utilizing an animal protein free extender (HTF®). Vitrification occurred by directly plunging a sperm suspension into liquid nitrogen. Sperm were assessed for motility, membrane integrity, acrosomal status and DNA integrity before and after cryopreservation. With both techniques, there were similar post-thaw/warming results (P > 0.05) with respect to progressive motility, kinetic variables VCL, VSL, VAP and BCF, DNA fragmentation, sperm membrane functionality and morphological abnormalities. Total motile sperm, progression ratios LIN, STR, and WOB, the ALH, sperm viability and sperm with intact membrane and acrosome were greater (P < 0.05) in the conventional frozen-thawed sperm than vitrified-warmed sperm. Plasma testosterone concentrations varied from 0.0 ng/mL to 7.7 ng/mL. For epididymal sperm, sperm motility and viability following thawing were greater in vitrified-warmed samples than conventionally-frozen samples; however, small sample numbers precluded statistical analysis. When considered together, these results indicate vitrification may be a possible alternative for wolf sperm cryopreservation.

Recent advances in donkey sperm vitrification

Artificial insemination (AI) with cryopreserved semen is an important tool to preserve endangered species, including European donkey breeds. Sperm vitrification is an alternative method to conventional freezing using high cooling rates and non-permeable cryoprotectant agents (CPAs). In donkeys, sperm vitrification was firstly developed in spheres by directly dropping the sperm (30 µl) into the liquid nitrogen. The vitrification media contained a combination of sucrose and bovine serum albumin as non-permeable CPAs and resulted in better sperm parameters after warming than extenders containing glycerol. Thereafter, sperm vitrification was optimized using an aseptic protocol, which consists of volumes up to 160 µl vitrified at 300 million sperm/ml using 0.25-ml straws with outer covers, obtaining similar sperm parameters as conventional freezing for total motility (52.7 ± 15.6% versus. 58.2 ± 16.1%), progressive motility (44.3 ± 15.0% versus. 44.7 ± 18.2%) and plasma membrane integrity (49.2 ± 11.2% versus. 55.4 ± 9.0%), respectively. In order to vitrify larger volumes of sperm, a procedure using 0.5-ml straws was evaluated; however, this methodology failed when compared to conventional freezing or other vitrification protocols, obtaining poor sperm quality after warming. Recently, a new methodology was developed for warming 0.25-ml straws in a water bath and after AI using the vitrified sperm, the uterine inflammatory response solved faster, and pregnancy rates were greater (22%) than frozen semen (10%) but not statistically different. In conclusion, all these findings confirm that sperm vitrification can be performed in donkeys as an alternative to conventional freezing for AI in jennies.