Characterization of loin shape from Duroc and Duroc composite finishing gilts

Gilts (n = 45) were used in this study to characterize the effect of genotype on loin characteristics and quality over the length of the loin. Three diverse genotypes included a high quality Duroc line (A), a Duroc based composite line selected for lean growth (B), and an F1 cross of the two (C). After harvest, bone-in loins were removed from the carcass and cut perpendicular to the backbone at the 5th/6th rib, 7th/8th rib, 10th/11th rib, last rib, midlumbar, and the loin/sirloin juncture. Quality measurements were obtained at the 5th/6th rib, 10th/11th rib, and the loin/sirloin juncture. Digital images were taken of each surface (n = 6) and analyzed for the determination of loin muscle area (LMA), muscle width, muscle depth (at three locations across the loin face), and fat depth. The average loin depth was calculated and used to calculate the loin depth:width ratio as an indication of loin shape or conformation. Loins from line A had the lowest (P < 0.05) subjective color score, had the highest (P < 0.05) amount of marbling, and were the firmest (P < 0.05) of all three lines. There were also differences (P < 0.05) between genetic lines for LMA, width, all three depths, fat depth, and depth:depth ratios. The most posterior portions of the loin had the largest (P < 0.05) LMA, loin width, fat depth, and muscle depth 1. However, the more anterior portions of the loin had greater (P < 0.01) values for the depth:width ratio and muscle depth:depth ratios.