35 Inter- and intra-stallion analysis of the kinematic sperm subpopulations in fresh ejaculates of Pura Raza Española horses
Y. Pirosanto A B , E. Teran A B , A. Molina C , J. Lavitola A and S. Demyda-Peyrás A DA Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina
B IGEVET (UNLP-CONICET), Facultad de Ciencias Veterinarias UNLP, La Plata, Buenos Aires, Argentina
C Departamento de Genética, Universidad de Córdoba, Cordoba, Cordoba, España
D CONICET, CCT La Plata, La Plata, Buenos Aires, Argentina
Reproduction, Fertility and Development 35(2) 143-143 https://doi.org/10.1071/RDv35n2Ab35
Published: 5 December 2022
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
The Pura Raza Española (PRE) breeding system is based on the intensive use of artificial insemination. Stallions are known for an extensive variability in semen quality, as some individuals are not suitable for gamete cryopreservation. This fact limits their use as breeders, particularly outside the farm or country. Different sperm subpopulations (SP) have been identified in horses’ ejaculates based on the motility characteristics displayed by individual spermatozoa. Several studies have demonstrated that, using computer-assisted sperm analysis (CASA) systems, it is possible to identify and quantify different sperm subpopulations within an ejaculate with specific patterns of movement due to its objectivity and repeatability. In this study, we aim to determine the existence of subpopulations in PRE stallions based on sperm kinetic data obtained from CASA. Semen samples were collected for one year, from February 2021 to February 2022, using an artificial Missouri vagina. We performed the kinematic characterisation of 141 fresh sperm samples from 24 PRE stallions using CASA. We determined eight different parameters in 239,546 spermatozoa, including: curved line velocity (VCL, μm/s), velocity average path (VAP, μm/s), velocity straight line (VSL, μm/s), amplitude of lateral head displacement (ALH, μm), beat-cross frequency (BCF, Hz), linearity (LIN, VSL/VCL × 100), righteousness (STR, VSL/VAP × 100) and oscillation (WOB, VAP/VCL × 100). Thereafter, we performed a principal component analysis (PCA) followed by a hierarchical and nonhierarchical clustering procedure to assign each spermatozoon to a given subpopulation. Finally, differences among individuals and ejaculates were analysed using a GLM statistical test, where the dependent variable is the proportion of the individual corresponding to each subpopulation and the individual and ejaculates were used as a fixed factor. Results showed that PCA clustering based on velocities (VAP and VSL) explained 46% of the variation, whereas PCA analysis based on linearity and head oscillation (LIN and ALH) accounted for 34%. These results allowed for the clustering of the spermatozoa in three kinematic subpopulations: fast and progressive (SP1), fast but nonlinear (SP2), and slow (SP3). Statistical differences were observed (P < 0.05), suggesting that different stallions have distinctive kinematic subpopulation patterns. This is particularly important in the analysis of SP1 (fast and progressive sperm), since it was associated with field fertility in previous studies. In addition, we determine the existence of differences within individuals, for which a careful characterisation of each individual is necessary to obtain reliable conclusions.
