Effects of Increasing Slaughter Weight on Production Efficiency and Carcass Quality of Finishing Gilts and Barrows

A total of 582 gilts and barrows were analyzed to investigate the regressive relationships to slaughter weight (SW) of variables related to production efficiency and pork quality. Average initial weights and SW were 88.6 and 122.5 kg, respectively, for gilts and 88.7 and 121.4 kg, respectively, for barrows. Average daily gain and gain:feed ratio were not affected by SW. Backfat thickness, which was significantly greater (p＜0.01) in barrows (23.3 mm) than in gilts (20.7 mm), increased with increasing SW (0.21 mm/kg; p＜0.001). When the 4-notch carcass yield and quality grades were quantified according to an arbitrary 1 point-per-1 notch scale, the former, but not the latter, regressed on SW (-0.64/10 kg; p＜0.01). The percent yield of the belly per total lean (overall mean=20.7%) increased with increasing SW (0.37%/10 kg; p＜0.001), whereas in other cuts, the SW effect was negligible. The redness of the loin also increased with increasing SW (p＜0.05), but other physicochemical characteristics were minimally influenced by SW. In sensory evaluation, effects of SW for fresh and cooked loin, ham, and belly were mostly considered insignificant in terms of quality, albeit statistically significant in several cases. However, positive regressions on SW (p＜0.01) of the marbling and acceptability scores of fresh loin as well as the fat:lean ratio of fresh belly were noteworthy. Collectively, SW of approximately 125 kg was maximal for both sexes under the current carcass yield grading, in which 94 kg is the upper weight limit for grade A carcass. However, if the carcass weight limit of the grading was to be removed or broadened, the SW for gilts (but not that for barrows because of their excessive fat content at above 125-kg SW) could be increased to 135 kg or greater without compromising carcass quality.