Cryopreservation of Fighting rooster spermatozoa: effect of different concentrations of glycerol

Glycerol (Gly) is the cryoprotective agent (CPA) most widely used to cryopreserve rooster semen. However, its cryoprotection, toxicity, and efficacy may vary in different breeds of roosters (e.g.,fighting rooster). In this sense, this investigation evaluated the effect of different concentrations of Gly added to the Lake-Ravie extender on the kinetic variables and plasma membrane integrity (PMI, equivalent to viability) of rooster spermatozoa. A total of 42 semen ejaculates from 6 Spanish fighting roosters (collected in 7 weekly sessions) by dorsal massage technique were used to conform 7-pools. Each pool was divided into 6-aliquots and then 6 treatments were formed according to Gly concentrations: 0 (control), 2% (Gly-2), 4% (Gly-4), 6% (Gly-6), 8% (Gly-8), and 10% (Gly10). The samples were frozen in static liquid nitrogen vapors, and their post-thaw sperm quality was analyzed using the CASA system (SCA-2018®) and Fluorescence (PI). Results after thawing showed that total (MT, %) and progressive (MP, %) motilities were higher (P<0.01) with the Gly-8 treatment compared to the control group and the Gly-4 and Gly-6 treatments. Regarding the postthaw kinetics, the oscillation (WOB, %) and the beat-cross frequency (BCF, Hz) were higher (P < 0.05) in the Gly-6, Gly-8, and Gly-10 treatments compared to their control. Finally, the PMI (%) was greater with the Gly-8 treatment compared to the Gly-2 treatment (P<0.05) and the control group (P<0.01). In conclusion, the addition of 8% glycerol to the freezing medium produced better sperm cryosurvival based on higher kinetics and integrity of the plasma membrane of fighting rooster spermatozoa.