93 Zeta potential of equine sperm and its association with sperm quality
M. F. Orsolini A B , M. H. Verstraete A C , M. van Heule A C , D. Orellana A , A. Ortega A , S. Meyers B and P. Dini AA Department of Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Davis, CA, USA
B Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California Davis, Davis, CA, USA
C Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
Reproduction, Fertility and Development 34(2) 283-284 https://doi.org/10.1071/RDv34n2Ab93
Published: 7 December 2021
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
The use of in vitro embryo production (IVP) in the equine breeding industry, a practice that is currently limited to intracytoplasmic sperm injection (ICSI), has been expanding rapidly. It is known that sperm quality affects developmental outcomes of IVP. Therefore, it is essential to explore novel techniques for characterising “high-quality” sperm and subsequent selection of highly fertile sperm for IVP. In this study, we aimed to characterise equine sperm net negative surface charge, estimated by zeta potential, and identify its associations with known measures of sperm quality. Ejaculates (n = 12) were partitioned for fresh (23°C, 0 h; n = 7) and cooled (4°C, 24 h; n = 5) processing by swim-up, density gradient centrifugation, density gradient-swim up, and microfluidic chip. Motility, viability, morphology, and zeta potential (Nano ZS, Malvern) were evaluated for both unprocessed fractions and post-selected fractions. Data were tested for normality and heterogeneity of variance. Non-normally distributed data were quantile transformed. Quality parameters were compared among groups by ANOVA, and associations between zeta potential and other measured parameters were assessed by Pearson correlations. For all analyses, P < 0.05 was considered significant. There were no differences in zeta potential between fresh and cooled samples (P = 0.89); thus, data were combined and averaged from all treatments to obtain an overall average of −12.72 ± 1.75 mV (mean ± s.d.; −8.48 to −16.34 mV, min-max). In addition, there were correlations between zeta potential and motility (r = −0.48; P < 0.0001), progressive motility (r = −0.49; P < 0.0001), and sperm viability (r = −0.33; P < 0.01). There were no correlations between zeta potential and percent normal morphology (P > 0.05). In conclusion, we identified an average net negative zeta potential on equine sperm and correlations between zeta potential and other measures of sperm quality. This aligns with previous studies of zeta potential for human sperm, for which zeta potential-based selection techniques have already been developed. Therefore, to improve sperm selection for equine IVP, future studies should focus on the adaptation and development of a novel method of sperm selection based on zeta potential.
