The aim of this study was to evaluate the physical and morphological characteristics of the sperm-rich fraction of jackass semen. To this end, 130 ejaculates from five Pêga jackasses were collected using an open model artificial vagina. The sperm-rich fraction was collected using the split-ejaculate method and assessed for the number of mounts/ejaculate, for physical and morphological characteristics of the semen and number of doses produced/ejaculate. It was observed that all characteristics evaluated differed among the five jackasses, except for the head defect rates. The mean values obtained for the jackass sperm-rich fraction collected were: number of mounts/ejaculate - 1.27; semen volume - 20.21mL; motility - 84.53%; vigor - 4.46; motility after dilution - 80.10%; sperm concentration/mL - 894.38 x 106; total sperm/ejaculate - 16.14 x 109; number of insemination doses/ejaculate (400x106 motile sptz) - 33.39; number of insemination doses/ejaculate (800 x 106 motile sptz) - 16.69; and percentage of normal sperm - 90.46%. Thus, in the present experiment the split-ejaculate method using an open artificial vagina worked well with the jackasses, and the sperm-rich fraction of the ejaculate of Pêga jackasses had high quality and sperm concentration, allowing its use for semen processing without reducing the number of insemination doses produced per ejaculate.
jackass; split-ejaculate method; sperm-rich fraction