Evaluation of Cryoprotective, Cryocapacitation Inhibitory and Fertility Enhancing Potential of RU-486, Sericin and Taurine in Cattle and Buffalo Semen

Background: Artificial insemination with frozen semen is of great value for livestock breeding and improvement. However, the procedure of cryopreservation leads to varying degree of oxidative and cryodamage to sperms deteriorating its quality, capacitation status and fertility. Hence, a variety of protocols, cryoprotectants and additives have been tried to protect sperms from such damages. This study was aimed to evaluate the antioxidant and cryocapacitation inhibitory potential of Mifepristone, Sericin and Taurine in routine extender on cryopreserved bull semen including in vivo fertility.
Methods: Semen ejaculates of 3 Gir and 3 Murrah bulls with >75% initial motility were split-diluted @ 100 million spermatozoa ml-1 using TFYG extender without and with Mifepristone (10 mu g/ml), Sericin (5 mg/ml) and Taurine (4 mg/ml) and frozen in LN2 using a programmable biofreezer. The freshly diluted as well as frozen-thawed samples were assessed for sperm motility, viability, plasma membrane integrity, CTC (chlortetracycline) fluorescence assay and seminal plasma oxidative markers. The straws frozen as above were used to inseminate 100-375 cows and/or buffaloes with each treatment involving well trained field AI technicians. Conception rates were determined based on confirmation of pregnancy per-rectum 45-60 days after first AI in non-return cases.
Result: The mean percentages, on dilution and at post-thaw stage in particular, of motile, live, HOS reactive and non-capacitated sperm were significantly (p<0.01) higher with reduced lipid peroxidation (MDA, SOD and GPx) whereas capacitated and acrosome reacted sperm were lower in Mifepristone supplemented extender than in control extender and the values for Sericin and Taurine fortified extender were intermediary in both the species. The first AI conception rates obtained for Gir and Murrah bull semen cryopreserved in control extender and extender supplemented with Mifepristone, Sericin and Taurine were 44.48, 51.11, 47.22 and 48.72% in cattle and 44.44, 55.40, 51.57 and 52.05% in buffaloes, respectively, suggesting that all additives used and Mefipristone in particular can be advantageously incorporated in the semen extender for cryopreservation of both cattle and buffalo semen.