Cryopreservation effect on sperm viability, mitochondrial membrane potential, acrosome integrity and sperm capacitation of alpaca spermatozoa detected by imaging flow cytometry

Eighty-five sperm samples were cryopreserved and SYBR14/PI, MitoTracker Deep Red FM, FITC-PSA/PI and chlortetracycline were used for imaging flow cytometry evaluation of sperm viability, mitochondrial membrane potential (MMP), acrosome integrity and sperm capacitation, respectively. Sperm motility was also registered. Sperm motility (46.1 ± 7.7 vs. 24.1% ± 6.5%), sperm viability (49.8 ± 11.5 vs. 32.3% ± 9.6%) and high MMP (49.8% ± 12.4% vs. 34.9% ± 9.9%) decreased significantly (p < .05) during cryopreservation process, in contrast to acrosome-reacted in viable spermatozoa (1.0% ± 1.6% vs. 1.0% ± 1.0%) and sperm capacitation (10.0 ± 9.8 vs. 8.2% ± 12.4%) that were similar (p > .05) before and after cryopreservation. Positive correlations were found between sperm motility versus high MMP (r = .63), sperm motility versus sperm viability (r = .67) and sperm viability versus high MMP (r = .88). In conclusion, cryopreservation of alpaca spermatozoa is related to a decrease in sperm motility, sperm viability and high MMP, meanwhile acrosome integrity and sperm capacitation are not affected.