BeyondⓇ extender in donkey semen: evaluation at 5 °C and 17 °C over 7 days

Abstract

The objective of this study was to evaluate the ability of the equine commercial extender Beyond^Ⓡ, both alone and with the addition of fresh egg-yolk (EY), to maintain donkey sperm motility, viability and acrosomes at 5 °C and 17 °C over 7 days or until progressive motility (PM) was lower than 20%. Fifteen ejaculates from 5 fertile jacks were diluted in EquiPlusTM, incubated 30 minutes at room temperature, centrifuged and resuspended in: Beyond^Ⓡ(B), B with 2% EY (BY) and skim milk-based extender with 2% EY (KY). Sperm kinematic parameters (CASA; AndroVision^Ⓡ) and viability and acrosome integrity (FITC-PNA/PI using flow cytometry; BD FACSCanto II^Ⓡ) were evaluated daily. Either ANOVA or Kruskal Wallis was used to analyze the data and P<0.05 was considered significant. In the samples at 5 °C a significant decrease in % PM was observed between day 7 (B: 34.18±8.0; BY: 36.14 ±17.9; KY: 30.08±0) compared to 24h (B: 50.04±20.8; BY: 59.19±20.4; KY: 63.29±17.1). At 72h significantly higher percentages of total motility (TM) were observed for B and BY compared to KY. PM in B was not significantly different to BY and KY at each evaluation time. However, the number of samples with PM > 20% at day 7 were greater in the BY samples (9/15) compared to B (5/15) and KY (1/15). Additionally, a significant decrease in live acrosome intact (LAI) sperm was observed on day 7 (B: 19.55±15.63; BY: 9.99±10.03; KY: 36.79±0) compared to 24h (B: 43.24±19.18; BY: 55.56±16.96; KY: 61.89±12.26). No significant differences were observed in % LAI for B compared to BY and KY at each evaluation time. At 17 °C, a significant decrease in percentage PM was observed on day 7 (B: 33.5±11.55; BY: 36.69±8.6) compared to 24h (B: 60.47±15.1; BY: 65.57±13.1). TM and PM in B were not significantly different to BY at each evaluation time. The number of samples with PM > 20% at day 7 was greater in the BY samples (9/15) compared to B (3/15). Additionally, % LAI was significantly lower on day 7 (B: 26.67±28.82; BY: 14.49±14.65) compared to 24h (B: 45.40±28.68; BY: 48.39±28.83). No significant differences were observed in % LAI for B compared to BY at each evaluation time. No significant differences were observed in any of the sperm parameters between both temperatures (5 and 17 °C) for any of the extenders assayed. To conclude, although Beyond^Ⓡ can be used to preserve donkey semen for 7 days, both at 5 and 17 °C, it is noteworthy that many more samples lasted 7 days with PM > 20% when extended in Beyond^Ⓡ with 2% egg-yolk.