Evaluation of the Impact of the Magnitude of Errors in the Sorting of Pigs for Market on the Optimal Market Weight

The objective was to estimate the impact that the accuracy in which pigs are sorted for marketing has on the optimal market carcass weight (CW) and economic returns. Two types of errors were evaluated in a stochastic model, 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. Initially, pigs were marketed in 3 marketing cuts (MCUT), 25% at 169, 25% at 179 and remaining 50% at 193 d of age. The timing of marketing was shifted in 7 d intervals with mean marketing ages of 155.5 to 211.5 d with mean CW’s of 75.7 to 108.7 kg. Sort loss was calculated using a market system for a U.S. pork processor (IPC, Delphi, IN). Mean for sort loss ($/pig) values for the pigs in the barn were fitted to a polynomial function of mean CW for each combination of BWEE and PNVE. The increase in mean sort loss for each unit increase in CW above 93 kg increased as BWEE and PNVE increased. Pork production costs were estimated using an industry spreadsheet. A base price of $1.433/kg of CW was used to produce a small profit per pig. Lean premium (LPREM, $/100 kg CW) for gilts was estimated as: LPREM = 0.4665 – 0.00198 CW, kg (R² = 0.99) and for barrows was: LPREM = 0.4176 - 0.00216 CW, kg (R² = 0.99). The optimal CW’s to maximize profit/pig and daily returns above daily costs were estimated for each combination of BWEE and PNVE. With accurate sorting, (BWEE = 0, PNVE = 0%) the optimal mean age for the 3 MCUT strategy was 190.5 d (176, 186 and 200 d MCUTs) at a mean CW of 97.0 kg and profit of $3.35/pig. With less accurate sorting (BWEE = 8%, PNVE = 24%), the optimal mean age decreased to 184.5 d with mean CW of 93.4, and profit of $2.00/pig. The optimal market ages and CW’s decreased as the accuracy of sorting pigs decreased. The impact of inaccurate sorting of market hogs on the optimal market BW is impacted by several factors (marketing grid, feed costs, market prices etc.).