1986). The effects of fat thickness and sex on pig meat quality with special reference to the problems associated with overleanness 2. Laboratory and trained taste panel results. ABSTRACTEvaluations of meat quality were made of 300 carcasses, of average weight 58 kg, falling into three fatness groups, 8, 12 and 16 mm for P 2 fat thickness. There were equal numbers of entire males and gilts. An increase in fat thickness was associated with an increase in the firmness of loin and shoulder backfat, a reduced incidence of fat separation and changes in the composition of both muscle and backfat: the concentration of lipid increased and that of water decreased, more markedly in backfat. In addition, the concentration of collagen in backfat decreased. The loin joint was visually most attractive when P 2 was 11 mm, attractiveness decreasing below and particularly above this value. Eating quality of grilled chops was assessed in a representative subsample of 96 pigs falling into the 8-mm and 16-mm P 2 categories. The only statistically significant difference observed between these extremes of fat thickness was in juiciness which was lower in the leaner pigs; the correlation between juiciness score and m. longissimus lipid concentration ('marbling fat') was 0-31. Juiciness did not influence the assessment of overall eating quality which showed no association with fatness. Entire males of similar backfat thickness to gilts (12 mm P 2 ) had a higher concentration of water and lower concentration of lipid in backfat and slightly softer backfat. There were no differences in eating quality, or in the presence of abnormal odours or flavours, between entire males and gilts. These results confirm those obtained in butcher and consumer panel tests in the same carcasses.

No abstract

i

SummaryThe development and proportions of muscle, fat and bone were studied in 341 entire male and female Iron Age (European Wild Pig × Tamworth), Pietrain and Large White pigs ranging in live weight from 12 to 370 kg. The number of pigs was: Large White, 138 entire males and 112 females; Pietrain, 41 entire males and 31 females; Iron Age, eight entire males and 11 females. The breeds and sexes were compared in terms of the allometric growth coefficients of tissues (b) and of tissue weights at constant side weight and constant weight of total side bone.At the geometric mean for side weight (26·5 kg), Pietrain carcasses had the most muscle (16 kg), followed by Large White (15kg) and Iron Age (11 kg), but the least fat (6 kg). Large White and Iron Age carcasses had 7 and 12 kg of fat, respectively. Relative to side weight, the earliest maturing tissue, bone, was particularly slow growing in Iron Age pigs (b = 0·627) and relatively fast growing in Large Whites (b = 0·801). The opposite was true for fat, the latest maturing tissue, and consequently Iron Age (b = 1·345) and Large White (b = 1·164) pigs were identified as early and late maturing, respectively. Pietrains had a higher growth coefficient for fat relative to side weight (b = 1·249) and lower growth coefficient for bone (b = 0·713) than Large Whites. The difference in percentage fat between Pietrains and Large Whites decreased slightly between 65 and 120 kg live weight. In terms of tissue growth patterns, Pietrains therefore demonstrated early maturing characteristics compared with Large Whites, and it is possible that a low voluntary feed intake under ad libitum feeding conditions prevents them from expressing these characteristics in terms of percentage of fat in the side. Pietrains had a particularly high muscle:bone ratio (6·2 at the mean side weight) compared with Large White (5·2) and Iron Age pigs (5·3).The difference in carcass composition between entire males and females was breeddependent. Entire male carcasses were slightly leaner overall and had a lower muscle: bone ratio than those of females, but tissue allometric growth patterns were similar in the two sexes.

The effects of selection for low backfat thickness on tissue deposition in different body sites has been investigated in pigs. Eight castrated male and eight female pigs from each of the selection and control lines maintained at the University of Newcastle upon Tyne were used. One castrated male and one female from each line was killed at 15, 30, 45, 60, 75, 90, 105 and 120 kg live weight following ad libitum food consumption and fully dissected.There were only small effects of line on carcass composition, selected pigs having 120 g/kg more bone than controls at the mean side weight (P < 0-001) and 40 g/kg more lean (NS). At the same mean weight of subcutaneous fat, selected pigs had thinner backfat than controls (approximately 3 mm) over m. longissimus at the last rib and over the shoulder but not at the mid-rump or mid-back positions. There appears to have been a slight shift in the sites of fat deposition from above m. longissimus in the loin towards the mid-line and rump as a result of selection, even though mid-rump, C and K measurements were all included in the selection index. However, there was no difference between the lines in the weight distribution of subcutaneous fat between six regions and so these shifts must have been very localized. There was no difference between lines in the relationship between P 2 fat thickness and proportion of lean in the side.The effects of selection on the sites of deposition within tissues other than subcutaneous fat were small. In particular there was no evidence that selection has caused relocation of body fat from subcutaneous to the other sites.