PSII-A-7 - Evaluation of Technician Skill Level Effect on Ultrasonic Estimates of Body Composition in Feedlot Heifers

Abstract: The objective of this study was to evaluate technician skill level on ultrasonic estimates of body composition in feedlot heifers (n = 31) across different days. One unexperienced technician (UT1) and one experienced technician (UT2) took measurements of 12-13^th rib fat thickness (FTU), longissimus muscle area (REAU) and intramuscular fat thickness (IMFU) on Day 1 (98 days preharvest), Day 2 (42 days preharvest) and Day 3 (48h preharvest) with an IBEX EVO II ultrasound unit equipped with 3.5-MHz, 172-mm scanning width, linear-array transducer. Carcass fat thickness (FTC), longissimus muscle area (REAC) and Marbling Score (MS) were measured 24 h postmortem. Significant differences were observed between FTC and FTU for UT1 (p < .01) and REAC and REAU for UT1 (p < .01) on Day 3. No differences were detected between FTC, FTU, REAC and REAU for UT2 on Day 3. No differences existed for REAU between technicians on Day 1 (p = 0.4547) or Day 2 (p = 0.4937). Significant differences between technicians were observed on Day 3 (p < .05) for REAU. Pearson correlation coefficients (p < .01) were .79 and .59 between REAU and REAC for UT1 and UT2, respectively. No significant differences were observed between technicians on Day 1 (p = 0.6175), Day 2 (p = 1.0) or Day 3 (p = 0.0625) for FTU. Pearson correlation coefficients (p < .01) were .79 and .76 between FTU and FTC for UT1 and UT2, respectively. No significant differences were observed between technicians on Day 1 (p = 0.1716) or Day 2 (p = 0.0595) but were significant on Day 3 (p < 0.05) for IMFU. Pearson correlation coefficients (p < .01) were .69 and .68 between IMFU and MS for UT1 and UT2, respectively. These results indicate dependence of ultrasound image collection on technician skill and years of experience to achieve accurate predictions for carcass endpoints in beef cattle.