Submitted to: Professional Animal Scientist
Publication Type: Other
Publication Acceptance Date: 11/7/2005
Publication Date: 12/1/2005
Citation: Hendrickson, E.B., Kennedy, D.W., Aiken, G.E., Tabler, S.F. 2005. Case study: assessment of relationships between carcass traits and body measures at conclusion of background grazing. Professional Animal Scientist. 21:495-500. Interpretive Summary: Uniformity of penned cattle in feedyards is important because inconsistency in size and finish results in under- and over-finished cattle being harvested. Costly discounts are levied by packers on carcasses with excessive yield grades and weights not within a specified range. Current trend in the industry is to retain ownership of cattle through the feedlot and sell direct to packers. Cattlemen using this marketing approach can maximize profit by sorting cattle into groups that will finish in comparable period. Cattle typically are sorted by scoring body condition, but this method is subjective and accuracy depends on experience of the scorer. An experiment was conducted with two groups of yearling steers grazing cool- or warm-season pastures to determine relationships that carcass traits have with body size and condition measures taken at the conclusion of background grazing. A simulated sorting was performed with each body measure to assess consistency in separating economically relevant carcass traits (marbling score, hot carcass weight, carcass value) into low and high groups. Although the best relationships were shown using backfat thickness relative to body weight and body weight relative to hip height, sorting by body weight at the conclusion of grazing was most consistent in separating groups averaging low and high in the carcass traits. Body weight can be used as a simple and objective tool for sorting cattle into uniform groups at entrance into the feedyard.
Technical Abstract: Measures of body size and condition may be useful in sorting feeder cattle into uniform groups prior to entering the feedlot. Two groups of yearling steers were allocated to three pastures during either the cool- or warm seasons and placed on either low, intermediate, or high planes of nutrition with a corn-soybean meal supplement. Separate measures of hip height (HIPH), body weight (BW), ultrasound fat thickness (UFT), kg BW per cm HIPH (BW/HIPH), body condition score (BCS), and UFT/100 kg BW (UFT/BW) were taken at the conclusion of stocker grazing and compared with endpoint carcass traits. Correlations of carcass traits with HIPH and BCS were minimal and inconsistent. Combining cattle for the cool- and warm-season pastures showed that hot carcass weight (HCW), kilogram of retail product (KGRP), and value per carcass (VALCAR) were positively correlated with BW and BW/HIPH. Carcass backfat thickness (CFT) was positively correlated with UFT. Yield grade (YG) and % retail product (%RP) were negatively correlated with UFT. Reduced multiple linear regression equations containing BW/HIPH and UFT/BW had the greatest coefficients of determination (R2 > 0.45) for HCW, KGRP, and VALCAR. Simulated sorting by each body measured into lower and upper fifty percentile groups showed HCW and VALCAR to have the greatest differences between percentile groups with data sorted by BW. Results indicated that BW could be used as an objective sorting tool at the conclusion of stocker grazing and improve uniformity of penned cattle in the feedlot.