The influence of the proportion of Duroc genes on growth, carcass and pork eating quality characteristics

A study Ic,as carried out involving 721 pigs, comprising boars and gilts, with either 0, 0.25, or 0.50 Duroc inclusion level, which were produced by mating Large White boars with Large White x British Landrace sows, Large White boars with Duroc x (Large White x British Landrace) sows, or Duroc boars with Large White x British Landrace sows, respectively Animals were reared on one of seven different feeding regimens from 30 to 90 kg live weight. Tissue growth rates were determined using a triple sampling procedure based on a combination of full-side and ham joint dissection on subsamples of pigs (127 and 366 rigs, respectively) and P-2 backfat thickness on the remainder. Initial body composition was determined at 30 kg on subsamples of the three genotypes. Daily food intakes increased with increasing Duroc inclusion but live-weight gains were similar for the three genotypes. Lean and fat growth rates and food conversion ratios were greatest for the 0.50 Duroc group, although the genotype differences were small. Killing-out proportions and P-2 fat depths were higher for the 0.25 and 0.50 Duroc groups. The proportion of lean in the carcass was lower (P < 0.01)for 0.50 Duroc pigs. Japanese colour scores and EEL reflectance indicated that the longissimus muscle was darker for the 0.25 and 0 50 Duroc genotypes. Subcutaneous fat firmness scores and penetrometer readings taken in the mid back indicated softer fat for the O Duroc group. Intramuscular fat levels increased (P < 0.01) with increasing Duroc inclusion (10.4, 11.2, and 18.2 g.kg for the 0, 0.25, and 0 50 groups respectively). Cooked longissimus from pigs with 0 50 Duroc had a lower shear force and was judged to have a stronger pork odour and to be more tender and acceptable than that from the 0 Duroc group. The 0.25 Duroc group showed a small improvement in tenderness but a weaker pork odour and similar overall acceptability compared with the 0 Duroc group. This study suggests that the use of the Duroc in crossing systems in the United Kingdom will have limited impact on growth performance but that 0.50 Duroc inclusion will result in fatter carcasses, higher intramuscular fat levels and improved eating quality.