Colloidal centrifugation with Androcoll-E prolongs stallion sperm motility, viability and chromatin integrity

The objective was to investigate the changes in stallion sperm quality (sperm motility, viability, membrane integrity and chromatin integrity) occurring during cool storage, and to study the effect of sperm selection by single layer colloidal centrifugation on these parameters of sperm quality. Spermatozoa from 3 stallions (10 ejaculates, 3-4 per stallion) were selected by centrifugation through a single layer of colloid (SLC). The resulting sperm preparations and the control samples (extended but unselected semen samples) were stored at 5 degrees C for 48h. Assessments of sperm quality, such as sperm motility, viability (SYBR-14/PI staining), membrane stability (Annexin-V/PI staining) and chromatin integrity, were performed on aliquots of the selected sperm preparations and unselected samples on the day of collection (3h) and after 24 and 48h of storage. In the SLC-selected sperm samples, sperm motility, sperm viability, proportions of spermatozoa with normal morphology and with intact chromatin were significantly better than in unselected samples (motility: 77+/-4% vs. 64+/-8% at 3h; P<0.001; viability: 79.5+/-9% vs. 64.7+/-9%, P<0.001; normal morphology 89+/-6% vs. 69+/-9%; chromatin integrity DFI 11.3+/-5% vs. 22.1+/-10%). Membrane stability, however, was not different in the SLC-selected and unselected samples (74.6+/-8% vs. 69.3+/-8%). The deterioration seen in sperm quality in the unselected samples was prevented by SLC, so that sperm viability, membrane stability and chromatin integrity were unchanged in the selected samples by 48h compared to 3h (P<0.001), whereas the unselected samples were significantly worse by 48h (P<0.001). Furthermore, it should be possible to send an aliquot of a normal insemination dose (i.e. unselected spermatozoa) overnight to a reference laboratory for analysis of both plasma membrane and chromatin integrity. In conclusion, centrifugation of stallion spermatozoa through a single layer of colloid is a useful technique for selecting the best spermatozoa from an ejaculate and, moreover, sperm quality is maintained during storage.