No abstract

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.

Jersey steers (n = 12) were used to evaluate the effects of an aggressive implant strategy aimed to improve value in historically low-value, dairy steers. Steers were fed for 420d after being randomly allocated to one of two treatments: IMP (Revalor-200 administered at d0-d70-d140-d210-d280-d350) or CON (negative control). Steers were harvested after 420d and were fabricated after chilling into primals, subprimals, and trimmed lean, fat, and bone components. Data were analyzed via independent t-test. Primals from IMP cattle were a greater percentage of round (P = 0.02; 22.93 vs 21.55%) whereas CON cattle were a greater percentage of rib (P = 0.01; 9.56 vs 8.81%) and plate (P = 0.06; 9.51 vs 8.43%). Subprimals were greater for IMP than CON in the brisket (P < 0.01; 2.55 vs 2.03%), bottom sirloin tri-tip (P = 0.04; 0.75 vs 0.64%), bottom round (P < 0.01; 3.23 vs 2.74%), and eye of round (P < 0.01; 1.35 vs 1.04%), with tendencies for differences in knuckle (P = 0.09; 3.01 vs 2.78%) and heel meat (P = 0.08; 1.20 vs 1.09%). Muscle to bone ratio was similar (P = 0.31) between CON (2.34:1) and IMP (2.54:1), whereas muscle to fat ratios were greater (P = 0.02) in IMP (4.05:1) than CON (2.68:1). Total carcass fat was greater in CON than IMP (P = 0.03; 20.19 vs 15.07%), total red meat yield was numerically larger in IMP than CON (P = 0.13; 59.02 vs. 53.88%), yet total bone was similar between treatments (P = 0.94; 22.97 vs 22.83%) cattle. These data indicate an aggressive implant strategy on Jersey steers can increase muscle to fat ratio and fabrication yields in the round and brisket, while reducing total carcass fat.

Improved reproductive management allowed dairy cow pregnancies to be optimized for beef production. The objective of this sire-controlled study was to characterize effects of maternal genetics and the dairy management system on calf growth. Pregnancies were created with a 2 × 2 factorial arrangement of dam breed (Holstein or Jersey) and mating type (artificial insemination or implantation of an in vitro produced embryo from a commercial beef cow oocyte). Resulting calves were reared in a calf ranch. Additionally, commercial beef cows were inseminated and reared resulting calves on range. Therefore, the five treatments were Angus × Holstein (A×H; n = 19), Angus × Jersey (A×J; n = 22), Angus × Beef gestated by Holstein (H-ET; n = 18), Angus × Beef gestated by Jersey (J-ET; n = 8), and Angus × Beef raised by beef (A×B; n = 20). Beginning at birth, calf body weight, cannon circumference, forearm circumference, top width, hip width, and hip height were measured approximately every 28 days until approximately 196 days of age. At birth, A×J calves weighed the least (P < 0.01). At 150 days of age, body weight was greatest (P < 0.05) among A×B calves, intermediate among H-ET and A×H calves, and least among J-ET and A×J calves (P < 0.05). Morphometric differences were detected between treatments (MANOVA P < 0.01). Primary discriminant function scores identified A×B calves having lesser values than A×J or A×H calves (ANOVA P < 0.01); A×B calves had greater cannon circumference, greater top width, and less hip height (standardized loadings of -0.47, -0.48, and 0.63, respectively). The dairy management system limited growth rate of beef genetics compared to the beef management system. In addition, Holstein dams transmitted greater growth potential than Jersey dams. Replacing maternal dairy genetics with beef genetics increased top width and decreased hip height.

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.