289 Sperm Quality Assessments Using Flow Cytometry do not Differ between Angus and Charolais Breeds of Yearling Bulls Meeting Breeding Soundness Exam Threshold Requirements

Abstract Flow cytometry has been used as a reliable and objective tool for bull sperm quality assessments and identification of sub-fertility. Our objective was to determine if breed differences exist in sperm quality assessments using flow cytometry when evaluating semen from yearling Angus and Charolais bulls that passed breeding soundness exam (BSE) semen evaluation thresholds. Ejaculates were collected via electroejaculation on one of three consecutive days from yearling (403.15 ± 11.19 d age) Charolais (n=23) and Angus (n=23) bulls as part of a BSE. BSEs were conducted by one veterinarian and all bulls met all requirements as set by the Society for Theriogenology. An additional sperm motility analysis was conducted with the iSperm analyzer. Ejaculates were diluted in BoviFree to 70 million cells/mL and sent overnight for flow cytometry analyses. Sperm flow cytometry analyses included: acrosome and cell membrane integrity, mitochondrial energy potential, and oxidation status. The GLIMMIX procedure of SAS with bull as experimental unit, bull breed as the main effect and collection date as a random variable was used to assess potential differences in sperm quality variables. Neither iSperm (P = 0.26) nor visual assessment (P = 0.66) of sperm motility differed among breeds. Bull breed did not influence (P = 0.83) total percentage of viable cells, nor percentage of viable cells with intact acrosomes (P = 0.83). When evaluating oxidation status by measuring reactive oxygen species, bull breed did not influence (P = 0.92) percentage of live sperm cells with positive reactive oxygen species status. There was a tendency (P = 0.10) for a greater percentage of sperm from Charolais bulls (31.1% ± 3.35) to have positive mitochondrial energy potential as compared with Angus bulls (17.6% ± 3.35). Bull breed appears to have little influence on sperm quality assessments among yearling bulls meeting threshold requirements for passing BSEs.