THE EFFECTS OF CROSS, SLAUGHTER WEIGHT AND HALOTHANE GENOTYPE ON LEANNESS AND MEAT AND FAT QUALITY IN PIG CARCASSES

Carcass and meat quality traits were studied in 94 barrows of known HA L-1843 genotype (homozygote-and heterozygote-+) from three crosses sla ughtered at 90 kg and 120 kg live weight. Crosses A and B were produce d from sires of which 0.5 of the genes were from a heavy-muscled X Lar ge White line and 0.5 from pure Pietrain (A) or Duroc (B). Sows for bo th A and B were from a hyperprolific Large White X Landrace line and t his latter line produced the pigs for cross C (control). The carcasses from cross A which were sired from boars having 0.75 of their genotyp e from heavy-muscled genetic lines had higher killing-out proportion, better conformation scores, greater loin depth and loin area, less car cass length and bone content, and greater lean proportion compared wit h cross C. The carcasses from cross B, with roughly 0.25 of Duroc gene s had a significantly higher backfat thickness than either cross A or C. However their composition was not significantly different from C, s ince the higher backfat was counter-balanced by their better conformat ion. Carcass and lean weight distribution was more favourable in cross es A and B, which had significantly higher economic yields than cross C. The halothane genotype did not have a significant effect on fatness and carcass composition, although the heterozygote showed a significa ntly greater muscle depth. In addition, no significant effect of the h alothane gene on carcass and lean weight distribution was observed. In relation to the light group of carcasses (72.8 (s.e. 4.4) kg), the he avy group (100.1 (s.e. 2.7) kg) had greater killing-out proportion, be tter conformation, longer carcasses, higher fatness and greater loin d epth and area. These genetic lines showed a 9.6 g/kg increase in fat a nd a 6.1 g/kg decrease in lean for every 10 kg of increasing slaughter weight. With the slaughter weight increase the longissimus dorsi musc le became less pale due to a higher muscle pigment concentration, and the backfat had a higher proportion of oleic and lower proportion of l inoleic and palmitic fatty acids. The halothane genotype had a signifi cant effect on meat quality. The heterozygote produced much paler, sof ter and more exudative meat. However, the effect of cross and carcass weight was not significant for meat quality measurements determining p ale, soft and exudative meat.