PSIII-8 - Sire breed differences for carcass attributes in feedlot steers using Ultrasound Technology

Live animal ultrasound measurements were taken on thirty-two feedlot steers and heifers for estimation of carcass endpoints including 12^th rib fat thickness (FTU), ribeye area (REAU) and intramuscular fat (%FatU). Ultrasound measurements were collected by an inexperienced technician using an Aloka 500 ultrasound unit using Beef Image Analysis (BIA) software. The objective of the study was to evaluate carcass differences of four sire breed types including Angus (n = 11), Ultrablack (n = 6), Nelore (n = 6), Braunvieh (n = 1) and Angus X Nelore X Braunvieh hybrid (n = 8). Carcass data collected at harvest included 12^th rib fat Thickness (FTC), Ribeye area (REAC), marbling score (MS), Yield Grade (YG), and Quality Grade (QG). The data were analyzed using SAS to determine breed effects. Means for FTU, FTC, REAU, REAC, %FatU and MS were 0.59 cm, 0.57 cm, 90.80 cm², 83.53 cm², 4.83%, and 483.75, respectively. There was no significant difference (P > 0.05) in YG and FT due to breed of sire. However, there was a trend for sire breed for ribeye area (P = 0.0728) for Angus X Nelore X Braunvieh cross and MS (P = 0.0786) for Ultrablack. Pearson correlation values between FTU and FTC, REAU and REAC, and %FatU and MS were 0.1217 (P = 0.05068), 0.3545 (P = .0465) and 0.5161 (P = 0.0025), respectively. These data suggest little differences existed in carcass attributes between various sire breeds out of a set of crossbred commercial cows.