Optimization of sperm freezability in Bactrian camel using various dilution rates and equilibration times

The effect of different dilution rates and equilibration times on the cryopreservation of Bactrian camel spermatozoa was evaluated in the current study. Semen samples from four healthy adult males were collected, processed and pooled. They were then subjected to a completely randomized 4×2 factorial design including four dilution rates (DR; 1:1, 1:2, 1:4 or 1:8; v:v with SHOTOR diluent) and two equilibration times (ET; 1 or 2 h at 5ºC). After freezing and thawing, sperm kinematic parameters as well as viability, plasma membrane integrity, abnormality and seminal malondialdehyde level were assessed. According to the results, four-fold diluted samples recorded significantly higher values (P < 0.05) for sperm total (39.58 vs 31.83 and 33.33,%) and progressive motility (19.50 vs 14.00 and 14.25,%), viability (55.37 vs 43.50 and 48.75,%) and plasma membrane integrity (46.75 vs 37.25 and 37.37,%) than those of both less (1:1) and high (1:8) concentrated samples, respectively. By contrast, the percentage of abnormal spermatozoa and the concentration of seminal malondialdehyde were comparable among all treated groups. Moreover, ET revealed that 1 h equilibration had significantly higher sperm motility (37.04 vs 33.33%), linearity (42.29 vs 32.26%), beat cross-frequency (13.15 vs 8.70 Hz), plasma membrane integrity (42.25 vs 39.75%) and viability (51.37 vs 48.12%) compared with 2 h of ET (P < 0.05). Taken together, a four-fold dilution along with 1 h equilibration can be an optimal procedure to cryopreserve Bactrian camel sperm.