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

A study Ic,as carried out involving 721 pigs, comprising boars and gilts, w ith either 0, 0.25, or 0.50 Duroc inclusion level, which were produced by m ating Large White boars with Large White x British Landrace sows, Large Whi te 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. T issue growth rates were determined using a triple sampling procedure based on a combination of full-side and ham joint dissection on subsamples of pig s (127 and 366 rigs, respectively) and P-2 backfat thickness on the remaind er. Initial body composition was determined at 30 kg on subsamples of the t hree genotypes. Daily food intakes increased with increasing Duroc inclusio n 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 gr oup, 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 prop ortion of lean in the carcass was lower (P < 0.01)for 0.50 Duroc pigs. Japa nese colour scores and EEL reflectance indicated that the longissimus muscl e was darker for the 0.25 and 0 50 Duroc genotypes. Subcutaneous fat firmne ss scores and penetrometer readings taken in the mid back indicated softer fat for the O Duroc group. Intramuscular fat levels increased (P < 0.01) wi th increasing Duroc inclusion (10.4, 11.2, and 18.2 g.kg for the 0, 0.25, a nd 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 D uroc group showed a small improvement in tenderness but a weaker pork odour and similar overall acceptability compared with the 0 Duroc group. This st udy suggests that the use of the Duroc in crossing systems in the United Ki ngdom will have limited impact on growth performance but that 0.50 Duroc in clusion will result in fatter carcasses, higher intramuscular fat levels an d improved eating quality.