PSI-12 - Comparison of body composition ultrasound versus carcass collection data, Warner-Bratzler shear force and ether extract testing on Beefmaster Steers.

Abstract: The objective of this study was to determine if ultrasound estimates of carcass quality traits could predict the final quality factors that influence consumers’ purchases. Beefmaster steers (n = 86) representing two different sires were ultrasounded 48d and 73d before harvest using an Aloka 500 ultrasound unit, equipped with a 17.2cm probe to collect 12^th rib fat thickness (BFU), 12^th rib longissimus muscle area (LMAU), intramuscular fat (%FATU) and rump fat (RFU). International Livestock Image Analysis (I.L.I.A) software (Harrison, Arkansas) was used for processing images to determine BFU, LMAU, %FATU and RFU using chute side captured ultrasound images on all steers. An Ultrasound Guidelines Council (UGC) field and lab certified technician captured all ultrasound images. Carcass data collection included 12^th rib fat thickness (BFC), 12^th rib longissimus muscle area (LMAC) and marbling score (MS). Additionally, Warner Bratzler shear force (WBSF) and Ether Extraction (EE) estimates were determined on 12-13^th longissimus muscle samples. All carcass data was collected by the Beef Carcass Research Center (BCRC) at West Texas A&M University. Data were analyzed using SAS version 9.4. Simple descriptive statistics were 1.03±0.26 cm, 88.8±8.61 cm², 5.02±0.93, 1.27±0.36 for BFU, LMAU, %FATU, and RFU, respectively. Simple descriptive statistics were 1.72±0.41 cm, 90.06±7.24 cm², 5.06.7±0.69, 6.08±1.92, and 3.34±0.79 kg for BFC, LMAC and MS, EE and WBSF, respectively. Pearson correlation coefficients were 0.71 (P < .0.001) between BFU and BFC, 0.42 (P < 0.0001) between LMAU and LMAC, and 0.35 (P < 0.001) between %FATU and MS. Pearson correlation coefficients were 0.42 (P < 0.001) between EE and %FATU and 0.59 (P < 0.0001) between EE and MS. These results suggest that ultrasound measures of final body composition should be taken closer to the final harvest date to better estimate endpoints of fat thickness, longissimus muscle area and intramuscular fat in harvest ready beef cattle.