A New Approach of Sperm Motility Subpopulation Structure in Donkey and Horse

Sabrina Gacem,Iván Yánez Ortiz,Jaime Catalán,Carles Soler,Jordi Miró,Anthony Valverde

doi:10.3389/fvets.2021.651477

Abstract

This study aimed to characterize the sperm kinematic values with high frames per second, to define the subpopulation structure of a horse and a donkey and compare them. A total of 57 fresh semen ejaculates (26 Spanish and 16 Arabian horse breeds and 10 donkeys) were collected and subsequently analyzed for kinematic parameters using the Computer-aided sperm motility analysis ISAS®v1.2 system and using a Spermtrack® 10-μm depth counting chamber. Sequences were recorded at 250 frames per second, and eight kinematic parameters were automatically evaluated. All kinematic parameters showed significant differences between a donkey and a horse and between horse breeds. All ejaculates evaluated showed excellent semen motility characteristics, with significantly higher values for all kinematic parameters for donkeys compared with horses except for beat-cross frequency. Donkey sperm was faster and linear than the horse. Regarding horse breeds differences, the Spanish horse had higher average path velocity, curvilinear velocity, and beat-cross frequency compared with the Arabian horse. Spanish horse sperm was rapid, but Arab horse was more linear. The principal component analysis showed three sperm subpopulations in the ejaculate of donkeys and horses with a significantly different motility characteristic between them. The dominant subpopulation for both donkey and horse was for rapid, straight, and linear with a high beat sperm (38.2 and 41.7%, respectively), whereas the lowest subpopulation was for the slowest and non-linear sperms. This, plus slight differences in the distribution of these subpopulations between Arabian and Spanish horses, were found. In conclusion, higher frames permitted to have a new interpretation of motile subpopulations with species and breed differences. More so, future works on donkey and horse breed spermatozoa should take into account differences between breeds that may interfere and alter the real analysis performed.

Highlights

All the present living species of equids are assigned to the genus Equus, sharing a common ancestor million years ago [1], being distributed worldwide in the most diverse environments
Our study aims to compare the distribution of these kinematic subpopulations between two close equid species horses and donkeys and two horse breeds Spanish and Arabian and that by using higher frames rate for sperm kinematic calculation
All the kinematic parameters showed significant differences between both species horse and donkey, being higher for donkey unless beat-cross frequency (BCF) was higher for the horse

Summary

Introduction

All the present living species of equids are assigned to the genus Equus, sharing a common ancestor million years ago [1], being distributed worldwide in the most diverse environments. The Equus genus comprises two lineages: the caballine, which includes domesticated horses (Equus ferus caballus), and the wild endangered Przewalski’s horse (Equus ferus przewalskii) of Mongolia, and Donkey/Horse Sperm Motility Subpopulations non-caballine grouping, which comprises the asses and zebras [2]. The domestication process for horses was initiated approximately 450 generations ago, assuming an average generation time of 12 years for wild horses, whereas that for donkeys was around 6,000 years ago [3]. The domestication process started with the need of humans to shape animals’ species according to their intentions, producing an artificial selection pressure. All the domestic species are quite far from the original in different aspects involving reproductive characteristics

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