Structural and functional characteristics of muscle fibres in pigs with different malignant hyperthermia susceptibility (MHS) and different meat quality

In pigs, intensive growth of the musculature is often accompanied by malign ant hyperthermia susceptibility (MHS; n gene) and poorer meat quality. Usin g histological and histochemical methods, different fibre characteristics i n the Longissimus muscle were found in Pietrain x German Landrace pigs with this gene defect. Compared to MHS homozygous negative pigs, groups with th e n gene had increased diameters of the mean fibre types and increased glyc olytic metabolic potential, as shown by a higher frequency of the fast twit ch glycolytic type and a lower frequency of the slow twitch oxidative fibre type. Differences between the groups were also found in the number of angu lar and giant fibre types. Furthermore, a positive correlation was found be tween the frequency of oxidative fibres and the relative enzyme activity of NADH tetrazolium reductase. The changes correlated with lower pH and highe r drip loss in meat from the MHS homozygous positive group. In conclusion, the different muscle fibre characteristics can be interpreted as endogenous factors which influence the physiological condition in the muscle of the l ive animal and meat quality post mortem. (C) 1999 Elsevier Science Ltd. All rights reserved.