An Analysis of Carcass, Ultrasonographic, and Projected Measurements of Feedlot Animals to Determine the Benefits and Accuracy of Harvest Groups Vs. Visual Selection

Ultrasonic measures of fat thickness (FTU) and percent fat (PFATU) were taken on Hereford steers (n = 49) and heifers (n = 2) ranging in age from 10 to 20 months in a production setting in central Missouri and used to evaluate carcass attributes and slaughter readiness. This information also included ultrasound weight (WgtU), projected fat thickness (EstFTU), projected percent fat (EstPFATU), projected harvest weight (EstWgt) and projected yield grade (EstYG). This data was used to sort animals into three harvest groups. Further information used in the analysis included: date of birth (DOB), feedlot in weight (WgtIn), feedlot mid-weight (MidWgt), days on feed (DOF), harvest date, age, rate of gain (ROG), harvest weight (HWgt), carcass weight (HCW), dressing percentage (Dress%), quality grade, fat thickness (FT), rib-eye area (REA), KPH (kidney, pelvic, heart fat), and yield grade (YG). The data was obtained from the Missouri Hereford Association and Manken Cattle Company. Data were sorted into three groups for analyzing, all data combined (ALL) (N = 51), data for animals harvested on correct projected date (CKD) (n =27), and data for animals not harvested on correct projected date (NCKD) (n = 24). Data were analyzed using MInitab for descriptive statistics, correlations, and multi-trait regression. The average EstFTU for CKD and NCKD were 1.12 cm and 1.08 cm respectively. By comparison, the average FT for CKD and NCKD were 1.31 cm and 1.08 cm respectively. The NumMS for CKD cattle was 5.07 compared to 4.62 for NCKD cattle. ALL cattle average grade was select plus, NumMS = 4.86. CKD cattle average grade was choice minus and NCKD average was grade select plus. CKD cattle had an actual YG of 3.04 and NCKD cattle had an actual YG of 2.83. The correlations between traits for CKD are considerably higher than the correlations for NCKD. Correlations for EstWgt and HWgt for CKD and NCKD were .86 and .52, respectively. This data indicates the cattle harvested on the correct projected date may have been able to perform closer to their optimum genetic potential compared to the cattle that were not harvested on the correct projected date