Chromatin and morphometry alterations of bovine sperm head after Percoll™ density gradient centrifugation

The aim of this work was to assess the morphometry and chromatin integrity of bovine sperm head after a three layers discontinuous Percoll™ density gradient centrifugation. Frozen semen doses were obtained from six bulls of different breeds, including three taurine and three Zebu animals. Three ejaculates per bull were evaluated. The semen doses were thawed and two smears were made from each sample before (control) and after the Percoll™ centrifugation (Percoll™ group). The smears were stained with toluidine blue and grayscale digital images were captured and processed in Scilab environment software. It was observed that chromatin heterogeneity was reduced (P < 0.05) and chromatin decondensation was increased (P < 0.05) after the Percoll™ treatment utilized. In addition, it was observed that sperm head length was higher (P < 0.05) and the side symmetry was lower (P < 0.05) in centrifuged sperm cells. When analyzed separately by subspecies, it was observed that the decrease (P < 0.05) in chromatin heterogeneity and the increase (P < 0.05) in chromatin decondensation occurred in Zebu sperm heads. In addition, the length and the width:length ratio of sperm heads was affected by Percoll™ centrifugation in Zebu semen. In conclusion, the three layers discontinuous Percoll™ centrifugation increased the chromatin decondensation and the morphometric alterations of frozen-thawed bovine semen. However, the real implication of these findings in fertility rates of centrifuged sperm must be investigated.