POTENTIAL USE OF VIDEO IMAGING AND REAL-TIME ULTRASOUND ON INCOMING FEEDER STEERS TO IMPROVE CARCASS UNIFORMITY

A study was conducted to evaluate two feeder cattle sorting systems fo r their ability to improve carcass backfat uniformity. One thousand an d thirty-one yearling steers (407 kg; SD = 46.2 kg) were assembled and processed at three Alberta feedlots. Each steer was weighed and ultra sonically assessed for backfat thickness and 1. dorsi area 88 to 154 d before slaughter. Rump height, frame score and muscle score were also recorded using an automated video imaging system, called the Musculo- Skeletal Imaging (MSI) Scanner. Sorting System 1 (MSI sorting system) used initial body weight, frame score and muscle score to hypothetical ly cluster animals into five ''predicted days on feed'' (PDOF) groups. Sorting System 2 (Oltjen sorting system) used initial body weight, ru mp height, backfat thickness, feeding inputs and a computer model of c attle growth to hypothetically cluster animals into five PDOF groups. Each sorting system was compared with the traditional system of visual ly sorting cattle at the end of the feeding period for its ability to reduce the variability in carcass backfat thickness. Steers were ident ified for slaughter when they reached the body weight and condition de sired by the feedlot manager. The MSI sorting system decreased the var iability in slaughter weight by 14.3% (P < 0.001), but had no effect o n the variability in carcass backfat thickness compared with the obser ved variability. The change in predicted net return resulting from the MSI sorting system varied between feedlot from $-4.09 to $8.82 head(- 1) slaughtered. The Oltjen sorting system increased the variability in slaughter weight by 33.9% (P < 0.001) and decreased the variability i n carcass backfat thickness by 15.5% (P < 0.001). The predicted net re turn from the Oltjen sorting system varied between feedlot from $-3.65 to $11.55 head(-1) slaughtered. Further work is required to determine the actual effect of sorting systems on feed efficiency, carcass qual ity and net return.