Assisted reproductive technologies (ARTs) are often extrapolated from horses to don-keys, despite poorer fertility outcomes in jennies, highlighting the need to identify spe-cies-specific traits to optimize ARTs in donkeys. This study compared, through histo-morphometry, the endometrium of jennies and mares. Endometrial biopsies were taken from reproductively sound jennies (n = 6) and mares (n = 6) in estrus. Histomorpho-metric analysis evaluated luminal (LE, µm) and glandular epithelium height (GE, µm), glandular lumen diameter (LD, µm), glandular area (GA, µm²), number of glands (#G), and glandular tissue percentage (GT, %), measured in the stratum compactum (SC) and spongiosum (SS). Results were statistically compared between species (jennies vs. mares), parity status (maiden vs. foaling), and stratum (SC vs. SS). Jennies exhibited higher (P < 0.05) values than mares for LE, LD-SC, GA-SC, and GT-SC. Greater glan-dular size and density in mares have been linked to susceptibility to endometritis, in-trauterine fluid accumulation, aging, and poorer reproductive outcomes in mares. These findings suggest that the histomorphometric features observed in reproductively sound jennies reflect anatomical differences that might contribute to a distinctive en-dometrial inflammatory response compared to mares. In conclusion, histomorphome-try revealed significant endometrial differences between mares and jennies, the latter displaying larger luminal epithelium, greater glandular size, and density than mares.

Preservation protocols for donkey sperm are based on those developed for horses, despite potential interspecific differences in cooling tolerance. This study compared horse and donkey sperm during long‐term storage at 5°C and 17°C. Ejaculates from four stallions and four jacks ( n = 16) were centrifuged, resuspended in skimmed milk‐based extender, and stored at both temperatures. Sperm motility, plasma and acrosome membrane integrity, and morphology were evaluated after 1, 2 and 7 days. Fresh semen parameters showed no interspecific differences ( p > 0.05). At 5°C, donkey sperm showed reduced motility and membrane integrity from Day 1, whereas horse sperm parameters remained stable at both temperatures up to Day 2. After 7 days, horse doses stored at 5°C maintained significantly higher quality. In conclusion, donkey sperm was more sensitive to storage at 5°C than horse sperm, highlighting the need for species‐specific preservation strategies.

The aim of this study was to evaluate the effect of silver nanoparticles (AgNPs) on donkey sperm parameters and their antimicrobial efficacy on bacteria isolated in the presence of antibiotics. Nine donkey ejaculates were collected and stored in a skim‐milk extender at different AgNPs concentrations (0, 0.01, 0.8, 1.6 and 3.12 mg/mL) at 5°C or 17°C. Sperm parameters, including total and progressive motility (CASA), plasma membrane integrity (PMI) and reactive oxygen species (rROS) production, were evaluated at 0, 24 and 48 h of storage. Additionally, bacteria isolated from donkey semen extended with antibiotics were exposed to AgNPs to determine the minimum inhibitory/bactericidal concentrations (MIC/MBC). Sperm motility parameters were higher at 17°C than 5°C after 48 h. AgNPs showed a dose‐ and time‐dependent cytotoxic effect, with concentrations ≥ 0.8 mg/mL significantly reducing motility, membrane integrity and increasing rROS after 24 h. AgNPs exhibited bactericidal activity at concentrations between 1.56 and ≥ 25 mg/mL. In conclusion, while liquid storage at 17°C is an effective strategy for preserving donkey semen, the use of AgNPs as a standalone antimicrobial is currently limited by their cytotoxicity at effective bactericidal doses.

The aim of this study was to evaluate the effect of uncoated, non‐functionalised magnetic nanoparticles (MNPs) on stallion sperm and to determine whether these effects depend on initial semen quality. Ten cooled ejaculates from 3 stallions were exposed to different MNP concentrations ([MNPs] = 0, 5, 25, and 50 mg/mL), agitated, and exposed to an external magnet to recover the unbound sperm fraction. Ejaculates were classified as high‐ or low‐quality groups according to initial evaluation sperm quality index (HSQi and LSQi), and the effect of [MNPs] was evaluated within groups using GLM. The 5 mg/mL concentration preserved sperm motility, membrane integrity and morphology regardless of initial sperm quality. In contrast, [MNPs] ≥ 25 mg/mL reduced sperm motility and recovery rate in both groups. These results indicate that the primary detrimental effect of MNPs is reduced sperm motility, consistent with observations in other species. In brief, nanopurification using 5 mg/mL MNPs can be used in high‐ and low‐quality ejaculates and may provide a useful reference for future nanopurification protocols in stallions.

Assisted reproductive techniques are often extrapolated from horses to donkeys, despite poorer fertility outcomes in jennies. This issue has been attributed to unknown uterine species-specific differences. This study compared, through histomorphometry, the endometrium of jennies and mares. Endometrial biopsies (N = 12) were taken from reproductively sound jennies (n = 6) and mares (n = 6) in estrus. Histomorphometric analysis evaluated luminal (LE, µm) and glandular epithelium height (GE, µm), glandular lumen diameter (LD, µm), glandular area (GA, µm²), the number of glands (#G), and glandular tissue percentage (GT, %), measured in the stratum compactum (SC) and spongiosum (SS). A total of 30 measurements of glandular size parameters and 10 fields of glandular density parameters per sample were recorded. Results were statistically compared between species (jennies vs. mares), parity status (maiden vs. foaling), and stratum (SC vs. SS). Jennies exhibited higher (p < 0.05) values than mares for LE, LD-SC, GA-SC, and GT-SC. These findings suggest that the histomorphometric features observed in reproductively sound jennies reflect anatomical differences that might partly explain previously observed species differences in post-breeding uterine response. In conclusion, histomorphometry revealed significant endometrial differences between species, with jennies displaying taller luminal epithelium, greater glandular size, and higher glandular tissue percentage in the SC than mares.

This study evaluated the effect of disaccharide supplementation on zebrafish sperm stored at 5°C for 24 h. Seven pooled replicates from 60 broodfish were used. Semen samples were initially cooled and, after 1 h, supplemented with either HBSS (E‐C), Sucrose 0.13M (E‐S13), Trehalose 0.13M (E‐T13) or Trehalose 0.26M (E‐T26). Sperm motility (computer‐assisted sperm analysis) and plasma membrane integrity (flow cytometry) were evaluated over 24 h of cool storage. During the first 2 h, E‐T26 decreased sperm motility values. After 24 h, E‐S13 and E‐T13 showed higher motility than E‐C and E‐T26. In conclusion, sucrose and trehalose supplementation improved sperm motility after 24 h of cold storage. Further studies are needed to assess the effect of disaccharide supplementation after shorter storage periods.