Effect of Duroc genes proportion on growth performance and on carcass and meat quality characteristics in heavy pigs

By means of the application of covariance models, the linear effects of the proportion of Duroc genes were evaluated with respect to growth (from 6 to 170 kg live weight) and feed/gain ratios, as well as carcass (lean cuts, adipose cuts, linear measures, backfat thickness, loin area and lean percentage) and meat quality (L* a* b* colour, reflectance, electrical conductivity, pH) in 167 heavy pigs (87 castrated males, 80 females) from different crosses of Duroc (D), Large White (LW) and Landrace (L) breeds, from 25 to approximately 300 d of age. The pigs were weighed at 25, 105, 170, 235 d and at the end of the trial (298 +/- 6 d of age), and were raised under the same conditions. The proportion of Duroc genes was 0% (LWxL; no. 33), 25% [(LWx(DxL); n. 31 and Lx(DxLW); n. 35)] and 50% [Dx(LWx(LWxL)); n. 68]. The increase in the proportion of Duroc genes negatively affected the live weight at the different ages (P < 0.05), but the weight at slaughtering was not affected (P > 0.10). In fact, during the final phase (from 120 to 170 kg l.w.) the effect of the Duroc breed on daily gain became positive (P=0.08), and the feed/gain ratios were significantly lower (P=0.02). The carcass composition was not significantly influenced by the increase in the proportion of Duroc genes, with the exception of a rise in the weight of neck (P < 0.01) and flare fat (P=0.02) and a reduction of ham (P=0.09). Carcass length resulted lower as the proportion of Duroc genes increased (P < 0.01); at 24 h from slaughtering, meat colour showed lower values for lightness (P=0.08), redness (P=0.02) and yellowness (P=0.03).