Evaluation of the Impact of Errors in the Sorting of Pigs for Market on Sort Loss at a Range of Marketing Ages

The BW growth curves for 25, 4000-head finishing barns were simulated to: 1) evaluate the impact of sorting errors on sort loss at different mean carcass weights (CW), and 2) demonstrate that the magnitude of sort loss due to inaccurate sorting is affected by the pigs’ mean CW. Two types of errors were evaluated, BW estimation error (BWEE) and percentage of pigs not visually evaluated (PNVE). Pigs are not evaluated when the targeted number of pigs are identified and sorting stops with heavier pigs than those sorted not being evaluated. Four levels of BWEE with SD’s of 0, 4, 6 and 8% of BW and 4 levels of PNVE (0, 8, 16, and 24%) were simulated. Sort loss was calculated using a market value system for a U.S. pork processor (IPC, Delphi, IN). Pigs were initially marketed in 3 marketing cuts, 25% at 169, 25% at 179 and remaining 50% at 193 d of age. Marketing ages for the pigs were shifted in weekly intervals with mean ages of 155.5, 162.5, 169.5, 176.5, 183.5, 190.5, 197.5, 204.5 and 211.5 d of age. Two variables: number of pigs with sort loss and mean sort loss per pig in the barn were fitted to a model including the fixed effects of level of marketing age (AGE), BWEE, PNVE, their interactions and random effect of replicate barn using the MIXED procedure of SAS^®. The main effects of AGE, BWEE, and PNVE, and AGE x PNVE, AGE x BWEE, and AGE x BWEE x PNVE interactions impacted both variables (P < 0.001). The effects of BWEE and interaction of BWEE x PNVE impacted (P < 0.001) both variables at all ages. The difference in sort loss/pig produced by the least accurate sorting (BWEE = 8% and PNVE = 24%) increased as the mean CW increased from $1.00 at 93 kg to $4.53 at 103 kg. Sort loss/pig increased more rapidly with increased CW at higher levels of BWEE and PNVE. The effect of inaccurate sorting to increase sort loss is minimized when the mean CW is close to the middle of the pork processor’s acceptable CW range and increases as CW increases to those approaching the upper acceptable CW range and is dependent on the marketing grid.