THE INFLUENCE OF TERMINAL SIRE GENOTYPE, SEX, SLAUGHTER WEIGHT, FEEDING REGIME AND SLAUGHTERHOUSE ON GROWTH-PERFORMANCE AND CARCASS AND MEAT QUALITY IN PIGS AND ON THE ORGANOLEPTIC PROPERTIES OF FRESH PORK

A total of 897 pigs were used in a study to investigate the relative e ffects of terminal slue genotype (lines A v. B v. C), sex (castrate v. gift), slaughter weight (80 v. 100 v. 120 kg), feeding regimen lad li bitum v. restricted, 0.82 ad libitum intake) and slaughter-house (H1 v . H2 v. H3) on growth performance, cal cass and meat quality character istics and the eating quality of fresh pig meat. Sire line A was a pur e Duroc population, and B and C were European-type experimental lines where C contained Pietrain and B did not. In fetal, 26 sires from line A, 42 sires from line B, and 21 sires from line C were mated to femal es from the same crossbred dam line and progeny were reared under stan dard conditions to slaughter. Following slaughter and carcass evaluati on, samples of longissimus dorsi were investigated for a range of meat quality and organoleptic characteristics. Line A produced fatter carc asses (C fat depths = 15.6 v. 14.0 v. 14.0 mm for lines A, B, and C, r espectively, average s.e. 0.39) with higher killing-out proportions (g /kg) (790 v. 779 v. 786 respectively, average s.e. 1.4) and higher vis ible marbling, less tissue separation, firmer backfat, and juicier (3. 81 v. 3.67 v. 3.71 respectively, average s.e. 0.044: on a scale 1 (ext remely dry) to 8 (extremely juicy)) and more acceptable meat (4.54 v. 4.37 v. 4.41 respectively average s.e. 0.037: on a scale 1 (dislike ex tremely) to 8 (like extremely)) with a lower shear force (5.35 v. 5.78 v. 5.67 kg respectively, average s.e. 0.078) than lines B and C which were similar in most respects. Increases in slaughter weight were ass ociated with a reduction in growth rate (785 v. 769 v. 725 g/day for 8 0, 100 and 120 kg slaughter weight respectively, average s.e. 8.5), in creases in backfat (C fat = 13.3 v. 14.1 v. 16.3 mm respectively, aver age s.e. 0.34) and longissimus muscle area (34.6 v. 40.7 v. 44.6 cm(2) respectively, average s.e. 0.59) and a deterioration in tenderness (4 .72 v. 4.40 v. 3.95 respectively, average s.e. 0.062: on a scale 1 (ex tremely tough) to 8 (extremely tender) and overall acceptability (4.65 v. 4.44 v. 4.25 respectively, average s.e. 0.045) and an increase in shear force (5.37 v. 5.58 v. 5.87 kg respectively, average s.e. 0.085) . Slaughter-house had a significant impact on pork odour scores but no t on other organoleptic properties. Pigs reared under ad libitum feedi ng grew faster (840 v. 678 g/day respectively, average s.e. 3.7), were fatter (C fat = 15.8 v. 13.2 mm respectively, s.e. 0.28), had lower c arcass yields (780 v. 790 g/kg respectively, average s.e. 1) and produ ced more tender, juicier meat than those reared under restricted feedi ng. Differences between castrated males and gilts in growth and cal ca ss trait were in line with other studies and there were no significant differences between the sexes for eating quality. There were relative ly few significant interactions (P < 0.05) for eating quality traits a nd most of these involved slaughter-house and were for pork odour inte nsity, which are of limited practical significance. This suggests that the effects of sire genotype, slaughter weight and feeding regimen on eating quality identified in this study are likely to be additive.