Abstract
Preservation of semen either by cooling or freezing results in structural and functional damage of spermatozoa. Exogenous antioxidants are added to semen extender to counteract this damage and enhance its preservability. This study was designed to evaluate effect of adding various concentrations of Royal jelly to tris-extender on bull semen characteristics after cooling and post-freezing. Methods: Pooled bull semen were extended with tris-citrate-fructose egg yolk diluent (control: 0% Royal jelly) and various concentrations of Royal jelly (RJ: 0.05%, RJ2: 0.1%, RJ3: 0.2%, RJ4: 0.3%). Extended semen was subjected slow cooling for 4 hrs, followed by freezing. Cooled and post-thawed semen was assessed for percentage of motility, alive, abnormality, membrane integrity, and acrosome morphology. Additionally, post-thawed semen was used for artificial insemination to assess its field fertility.
Results: In cooled semen, sperm motility percentage in the four concentrations of royal jelly was comparable to the control. Percentage of alive sperm was superior in the first concentration (RJ1). The second, third and the fourth concentrations (RJ2, RJ3 and RJ4) gave the best HOST percentage relative to the control. Acrosome integrity was the highest in the second concentration (RJ2), while the lowest was at the fourth concentration (RJ4) as compared to the control. Motility and percentage of alive spermatozoa in post-thawed semen was superior in (RJ1, RJ2) concentrations of royal jelly relative to the control. Also, sperm abnormalities were significantly reduced in (RJ1, RJ2). The HOST percentage was significantly higher in the fourth concentration (RJ4). Acrosome integrity was significantly higher in all concentrations and the best was in (RJ1, RJ2) compared to the control and other concentrations. Conception rate was the best in RJ1and RJ2. Conclusions: Addition of royal jelly to bull semen extender improved its quality during cooling and post-thawing.

Key words: Royal jelly, bull, semen quality, extender