Estimation of Final Carcass Composition Using Ultrasound, Warner-Bratzler Shear Force and Ether Extract Testing on Beefmaster Steers.

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) from two experiments representing two different sires were ultrasounded 48d and 73d before harvest using an Aloka 500 ultrasound unit, equipped with a 17.2 cm probe to collect 12th rib fat thickness (FTU), 12th rib longissimus muscle area (REAU), intramuscular fat (IMFU) and rump fat (RFU). International Livestock Image Analysis (I.L.I.A) software (Harrison, Arkansas) was used to process images to determine FTU, REAU, IMFU 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 12th rib fat thickness (FTC), 12th rib longissimus muscle area (REAC) and marbling score (MARBNum). Additionally, Warner Bratzler shear force (WBSF) and Ether extract (EE) were determined on 12-13th 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. Overall simple descriptive statistics were 1.03 ± 0.26 cm, 88.79 ± 8.61 cm2, 5.02 ± 0.93 %, 1.26 ± 0.36 cm for FTU, REAU, IMFU, and RFU, respectively. Simple descriptive statistics were 1.72 ± 0.41 cm, 90.06 ± 7.24 cm2, 50.5 ± 6.88, 6.08 ± 1.92, and 3.34 ± 0.79 kg for FTC, REAC and MARBNum, EE and WBSF, respectively. Pearson correlation coefficients for experiment 1 were 0.73 (P < 0.01) between FTU and FTC, 0.52 (P < 0.01) between REAU and REAC, 0.45 (P < 0.01) between IMFU and MARBNum, and 0.44 (P < 0.01) between EE and IMFU. Pearson correlation coefficients for experiment 2 were 0.73 (P < 0.01) between FTU and FTC, 0.32 (P < 0.01) between REAU and REAC, 0.31 (P < 0.01) between IMFU and MARBNum, and 0.33 (P < 0.01) between EE and IMFU. 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.