Kinematic Sub-Populations in Bull Spermatozoa: A Comparison of Classical and Bayesian Approaches

Abstract

The ejaculate is heterogenous and sperm sub-populations with different kinematic patterns can be identified in various species. Nevertheless, although these sub-populations are statistically well defined, the statistical differences are not always relevant. The aim of the present study was to characterize kinematic sub-populations in sperm from two bovine species, and diluted with different commercial extenders, and to determine the statistical relevance of sub-populations through Bayesian analysis. Semen from 10 bulls was evaluated after thawing. An ISAS®v1 computer-assisted sperm analysis (CASA)-Mot system was employed with an image acquisition rate of 50 Hz and ISAS®D4C20 counting chambers. Sub-populations of motile spermatozoa were characterized using multivariate procedures such as principal components (PCs) analysis and clustering methods (k-means model). Four different sperm sub-populations were identified from three PCs that involved progressiveness, velocity, and cell undulatory movement. The proportions of the different sperm sub-populations varied with the extender used and in the two species. Despite a statistical difference (p < 0.05) between extenders, the Bayesian analysis confirmed that only one of them (Triladyl®) presented relevant differences in kinematic patterns when compared with Tris-EY and OptiXcell®. Extenders differed in the proportion of sperm cells in each of the kinematic sub-populations. Similar patterns were identified in Bos taurus and Bos indicus. Bayesian results indicate that sub-populations SP1, SP2, and SP3 were different for PC criteria and these differences were relevant. For velocity, linearity, and progressiveness, the SP4 did not show a relevant difference regarding the other sperm sub-populations. The classical approach of clustering or sperm subpopulation thus may not have a direct biological meaning. Therefore, the biological relevance of sperm sub-populations needs to be reevaluated.

Predictive Capacity of Boar Sperm Morphometry and Morphometric Sub-Populations on Reproductive Success after Artificial Insemination

“…Several studies have described the presence of different sub-populations within an ejaculate [ 11 , 19 , 61 , 62 , 63 , 64 , 65 , 66 , 67 ]. These sub-populations may be affected by external factors associated with semen, such as extender type or species [ 68 , 69 ]. Even the sperm sub-population distribution can vary depending on the statistical multivariate procedure used [ 70 ].…”

Biotecnología aplicada al estudio de la movilidad del semen porcino

“…Los estudios futuros de la distribución de subpoblaciones en los eyaculados, deberían considerar diferentes enfoques con respecto a las especies y/o razas (líneas genéticas seleccionadas), la fuente de las muestras (epidídimo, semen en plasma seminal, espermatozoides diluidos en diluyentes comerciales, sexados o seleccionados por gradientes), el tipo de almacenamiento (enfriado o criopreservado) y aplicación (vaginal, sonda de inseminación intra-cervical, post-cervical o intrauterina). Se podrán presentar posibles patrones de subpoblación e interacción que aportarán otros significados en cada uno de estos contextos, por lo que la investigación debería orientarse a estudiar estos escenarios (Valverde et al, 2016;2019c;2019d;Víquez et al, 2020).…”

The application of computer-assisted semen analysis (CASA) technology to optimise semen evaluation. A review

“…Sperm motility (total and progressive) and concentration are the principal variables assessed at the AI centres or farms to calculate AI doses (Caldeira et al, 2019). For dilution of the sample species, specific extenders must be defined for both refrigeration and cryopreservation of the samples (Foote, 2002;Víquez et al, 2020). Cryopreservation-specific protocols for freezethaw, including vitrification, must be defined for each species (Yeste, 2016).…”