171 Association between Angus bulls breeding soundness exam classification and expected progeny differences

Bull selection is based on the animal’s phenotype and expected progeny differences (EPDs); however, there is no EPD directly associated with semen quality or the ability to pass a breeding soundness exam (BSE). The objective of this study was to investigate whether current EPDs reported by the American Angus Association were associated with BSE components and results (pass or fail). The same licensed theriogenologist performed all BSEs at The University of Tennessee Bull Development and Evaluation Program from the years 2019 to 2023 on yearling Angus bulls (n = 167; 430.3 ± 24.8 days old). Bull BSEs were performed according to the Society for Theriogenology Guidelines, and data for physical soundness, scrotal circumference, and semen quality (motility and morphology, with semen collected through electroejaculation) were assessed. Bulls were classified as a satisfactory potential breeder or unsatisfactory potential breeder (deferred bulls were considered as unsatisfactory for the purposes of this research). EPDs and Indexes (recognized by a $ in front of the abbreviation) were retrieved from the American Angus Association on April 24, 2024. We used the GLIMMIX function in SAS to test associations between BSE outcome for each EPD and Index. Further, Pearson correlation was used to assess the relationship between BSE components and each EPD and Index. Overall, 17% of bulls (n = 28) in our data set failed a BSE. On average, bulls that passed a BSE had lower (P = 0.01) residual average daily gain (RADG) and docility (DOC), and tended (P = 0.109) to have lower yearling weight (YW), feedlot value ($F), and beef value ($B) than bulls that failed; other EPDs were nonsignificant (P = 0.14). Scrotal circumference at BSE was positively correlated (P = 0.05) with weaning weight (WW), yearling weight (YW), residual average daily gain (RADG), dry matter intake (DMI), scrotal circumference (SC), mature weight (MW), mature height (MH), carcass weight (CW), weaned calf value ($W), and feedlot value ($F), and negatively correlated (P = 0.05) with claw set (CLAW) and cow energy value ($EN). Percentage of normal sperm was negatively correlated (P = 0.05) with weaning weight (WW), yearling weight (YW), residual average daily gain (RADG), and docility (DOC). Percentage of sperm head defect was positively correlated (P = 0.05) with yearling weight (YW), residual average daily gain (RADG), scrotal circumference (SC), and docility (DOC). Also, the percentage of sperm tail and midpiece defects was positively correlated (P = 0.004) with docility (DOC). In summary, we were able to identify correlations between BSE components and Angus bull’s EPDs; however, a larger data set, including actual bull phenotypes for non-BSE traits, is necessary to validate these findings.