Equivalent seminal characteristics in human and stallion at first and second ejaculated fractions

Abstract

Sperm quality was assessed in normozoospermic human (n = 10) and Spanish breed stallion (n = 10) after sperm fractionation during ejaculation. The first ejaculated frac-tion was separated from the second. A third sample was reconstituted using equiva-lent proportion of both fractions (RAW). Fraction 1, Fraction 2 and RAW semen were incubated for 30 min at 37°C to homogenise the impact of iatrogenic damage be-tween both species. Sperm concentration, motility and sperm DNA damage were as-sessed in each fraction and RAW semen. The results showed two important facts: (i) spermatozoa confined at Fraction 1 exhibit superior parameters than those included at Fraction 2 in both species, and (ii) there is a certain level of concordance between spe-cies in the proportion of benefit observed when Fraction 1 is compared to RAW semen. Altogether, these results call into question whether the standard practice of whole ejaculate collection can be considered the best strategy when using male gam-etes for artificial insemination. In fact, the reconstituted RAW semen exhibits poorer semen characteristics than those found in Fraction 1.