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This experiment was designed to quantify the empty body composition of Jersey steers administered an aggressive implant strategy. Jersey steers {n = 30; initial body weight (BW) 183 ± 43 kg} were randomly assigned to one of two implant strategies: negative control (CON), or implanted with Revalor 200 (200 mg trenbalone acetate / 20 mg estradiol 17-β; (REV) every 70 d (d 0, d 70, d 140, d 210, d 280, d 350) during a 420 d feeding period. Steers were harvested on d 421; 6 CON and 6 REV steers were randomly selected for collection of blood, hide, ground viscera, bone, and ground lean and fat to determine empty body composition. Proximate analysis was completed for each sample to determine total body percentages of moisture, crude protein, fat, and ash. Data were analyzed via independent t-test. Percentage empty body moisture (46.48% CON vs 49.69% REV) and empty body protein (15.32% CON vs 17.58% REV) were greater (P < 0.01) in REV cattle. In contrast empty body fat (33.51% CON vs 26.93% REV) was greater (P < 0.01) for CON cattle. Empty body ash did not differ (P > 0.10; 4.69% CON vs 5.80% REV) between treatments. Negative control steers contained a total empty body protein to total empty body fat ratio of 0.44:1 compared to 0.62:1 for REV steers. These data suggest that an aggressive implant strategy alters composition of gain during the finishing of Jersey steers toward increased protein and decreased fat.

Steers (n = 80; initial BW 271 ± 99) were serially scanned at 42-d intervals during a 378-d feeding period using an Aloka 500 device by a certified Ultrasound Guidelines Council (UGC) technician using real-time ultrasound. This included 10 separate ultrasound scanning sessions following the initial weight and ultrasound data taken on day minus 7 (one week prior to initial start date). Steers were randomly assigned to implant treatment (either implanted with Revalor XS or not) at day -7. Cattle were weighed and scanned for 12th-rib fat thickness (FTU), 12th-rib longissimus muscle area (LMAU), percentage intramuscular fat (%FATU), and rump fat thickness (RFU) to determine the ability of ultrasound to predict carcass grading outcomes at harvest. Scans were processed by CUP Lab technicians. Eight steers were harvested each 42 days. Carcasses were assessed 48h after harvest to determine 12th-rib fat thickness (FTC), 12th-rib longissimus muscle area (LMAC), and marbling score (MARB). Data were analyzed via Pearson correlation and linear regression to determine the relationship of ultrasound measures to carcass outcomes. Positive correlations (P < 0.01) between ultrasound measures taken the day before harvest and carcass measurements indicated strong relationships between FTU and FTC (r = 0.91), LMAU and LMAC (r = 0.93), and moderately strong relationships between %FATU and MARB (r = 0.76). Prediction equations were generated to estimate FTC = .0088 + (1.02585 x FTU), LMAC = 16.29720 + (0.77197 x LMAU) and MARB = 19.87510 + (5.19832 x %FATU). Results suggest real-time ultrasound data provides an effective tool to estimate carcass outcomes pre-harvest.