Reproductive biology of Pêga Jackasses : characteristics of sperm-rich fraction collected using the split-ejaculate method

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 10; total sperm/ejaculate 16.14 x 10; number of insemination doses/ejaculate (400x10 motile sptz) 33.39; number of insemination doses/ejaculate (800 x 10 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.