Long-Term Motility Of Semen Following Breeding Soundness Exams For Yearling Beef Bulls

Abstract To find an in vitro predictor of in vivoM/em> semen motility prompted this study. Our objective was to evaluate semen motility for an 8-hour period immediately following a breeding soundness exam. Ejaculates from 52 Angus and 56 Charolais bulls were evaluated. Motility, morphology, scrotal circumference and pH of ejaculate were evaluated at the time of collection. Ejaculates were then extended using a one to one ratio and incubated in a water bath held at 37 degrees Celsius and evaluated hourly. Motility was evaluated hourly for 8 hours, or until motility of the sample reached zero. Data were analyzed for breed and hourly effects using the GLIMMIX procedure of SAS. There was statistical evidence for difference (P < 0.0001) between breeds for motility over time. Angus ejaculates had higher pH values than Charolais ejaculates showing an association between breed and pH (6.82 vs 6.76, respectively). Primary spermatozoa abnormalities were greater (P < 0.0001) for Angus bulls compared to Charolais bulls (13.33% vs. 10.91%, respectively). Scrotal circumference between breeds tended to be different (P < 0.07), with Charolais bulls having a larger scrotal circumference compared to Angus bulls (38.29 vs. 38.03 centimeters, respectively). There was no difference (P > 0.05) between breeds for secondary abnormalities. There was a significant interaction (P < 0.01) between breed and time of motility measurement. Angus bull’s motility decreased drastically until hour 4, it then had a more gradual decrease until hour 8. Charolais bulls had a more gradual decrease in the percentage of motile sperm over time. In conclusion, there was evidence for difference between breeds for pH, primary spermatozoa abnormalities, and long-term motility, and a scrotal tendency. Understanding the effects of breed and individual biological factors may help producers adjust BSE expectations and lead to future research in long term semen motility.