Carcass characteristics and fat depots in Iberian and F1Large White × Landrace pigs intensively finished or raised outdoors in oak-tree forests1

A factorial experiment was performed with 117 barrows belonging to the Iberian (IB) and crossbred F1Large White × Landrace (F1) genetic groups, either intensively finished (IN) or finished outdoors on pasture in an oak and cork tree forest (EX). Information was collected on carcass weight, yield, and dimensions; weight of organs, carcass cuts, and abdominal fat depots; backfat depth; measurements of the longissimus thoracis (LT); and yield of different leg tissues. For the 41 slaughter and carcass traits analyzed, the interaction between genetic group and finishing system was significant (P< 0.05) in 18 traits, and overall, there was a more pronounced influence of genetic group than of finishing system. In most variables, particularly those related with fat deposition, the interaction reflected mostly changes in mean differences among genetic groups rather than in their ranking, where IB pigs consistently produced fatter carcasses, regardless of the finishing system. Liver weight in IB-EX pigs was lower by nearly 8% when compared with F1-EX or IB-IN pigs, but the opposite pattern was found in F1pigs, where liver weight in F1-EX pigs was higher by 16% relative to IB-EX pigs or to F1-IN pigs. The deposition of adipose tissue was much larger (P< 0.05) in IB pigs compared with F1pigs, with means for fat depots in IB pigs that were higher by about 25% in total abdominal fat, 94% in dorsal fat depth, 72% in intermuscular plus subcutaneous fat in the leg, and over 300% in intramuscular fat (IMF). The deposition of lean tissue was much lower in IB pigs (P< 0.05), with means for trimmed loin weight corresponding to about one-half of the means obtained in F1pigs, whereas lean percentage in the leg of IB pigs was about two-thirds of the mean in F1pigs and the mean area of the LT was nearly one-half of that observed in F1pigs in the same finishing system (P< 0.05). A strong correlation was observed between the various fat depots when the full data set was considered (correlations of IMF with abdominal fat and backfat depth of 0.65 and 0.83, respectively; P< 0.05), but the correlations were much smaller when they were estimated within breed, particularly for IB pigs (−0.10 and 0.20 for the correlations of IMF with abdominal fat and backfat depth, respectively; P> 0.05), indicating that it is feasible to reduce subcutaneous and abdominal fat without compromising IMF and meat quality.