Sperm motility subpopulations are correlated with fertility in Retinta bulls

TERAN ESTER; MOLINA ANTONIO; RAMON MANUEL; PIROSANTO YAMILA; DEMYDA-PEYRÁS, SEBASTIÁN

Savannah

Congreso; 48th international Embryo Tecnology Society; 2022

Mammalian sperm are characterized by the presence of subpopulations, which have been proposed to have adaptive and functional roles. These subpopulations are characterized by distinct morphometric and kinetic parameters; therefore, their relative abundance could explain changes in fertilization potential of individuals. Our objective was to establish a relationship between sperm motility subpopulations and fertility in Retinta bulls. Motility of frozen-thawed sperm was assessed after thawing, using computer-assisted sperm analysis (CASA) to evaluate different speed parameters including curvilinear velocity (VCL), straight-line velocity (VSL) and average path velocity (VAP); trajectory indexes, including percentage of linearity (LIN), percentage of straightness (STR) and wobble coefficient (WOB); and two other parameters related to the impulse force of the flagellum at the head: mean amplitude of lateral head displacement (ALH) and beat-cross frequency (BCF). A principal component analysis was performed and variables VAP, LIN, ALH were chosen for a non-hierarchical clustering followed by a hierarchical clustering that finally assigned each sperm to a subpopulation based on the similarity of their values. Four subpopulations with specific kinetic features were determined. Subpopulation 1 were fast and progressive sperm with high VCL, VAP, LIN and ALH. Subpopulation 2 consisted of medium and progressive sperm, with lower VCL and VAP, and intermediate LIN and ALH. Subpopulation 3 was the slowest and non-progressive sperm and had the lowest values for speed, LIN and ALH. Finally, Subpopulation 4 were hyperactivated and non-progressive sperm, characterized by the highest VCL and ALH values, high VAP, and low LIN. Fertility values of 37 bulls were obtained using the Reproductive efficiency parameter (Re) breeding values, estimated using a mixed model implemented in the BLUPF90 family programs from a dataset of 67457 calving records from 11645 individuals. Spearman correlations were performed between percentage of each subpopulation and fertility values. There was a moderate significant negative correlation (r=-0.33, p0.05). In conclusion, proportions of subpopulations could be used to predict fertility of cattle sperm, perhaps including the ability to identify samples with low fertility.