Changes of the activities of glycolytic and oxidative enzymes before and after slaughter in the longissimus muscle of Pietrain and Duroc pigs and a Duroc-Pietrain crossbreed1

Abstract

After slaughter of pigs, the pH of the meat decreases due to lactate accumulation within the tissue. In addition to calcium homeostasis, energy metabolism plays a key role during the muscle-to-meat transition, and it is interesting to know how specific enzymes of the glycolytic and oxidative pathways change during this process, especially in relation to the antemortem situation, and if there is an impact of these alterations on the meat quality characteristics. Therefore, in the present study samples of the LM from the pig genetic groups Pietrain (Pi), Duroc (Du), and a Du × Pi crossbreed population (DuPi) were collected 24 h before as well as 1 min, 40 min, and 12 h after slaughter, and the activities of the glycogen phosphorylase (GP), phosphofructokinase (PFK), lactate dehydrogenase (LDH), citrate synthase (CS), NADH-ubiquinone oxidoreductase (complex I), and cytochrome oxidase were analyzed. Additional investigations include carcass and meat quality characteristics as well as the microstructure of the LM. The Pi breed had greater (P < 0.05) carcass yield and lean meat values, but no differences (P > 0.05) of the meat quality traits could be determined between the investigated pig breeds. The Pi pigs exhibited a greater (P < 0.05) percentage of fast-twitch glycolytic and had smaller amounts (P < 0.05) of slow-twitch-oxidative fibers in comparison with the Du pigs. The enzyme activities of the GP, PFK, and complex I increased (P < 0.05) immediately after slaughter (1 min postmortem) of the pigs and the activity of the LDH within 40 min postmortem. After 12 h, the GP, PFK, LDH, and complex I activities decreased to the amount of the preslaughter sample. No differences could be found with regard to the enzyme activities of the CS and cytochrome oxidase at all determination times. Considering the enzyme activities within the different breeds, the Pi pigs exhibited greater (P < 0.05) GP and PFK and the Du animals exhibited greater (P < 0.05) CS and complex I activities. The study indicates that the glycolytic enzymes GP, PFK, and LDH as well as the complex I influence the muscle-to-meat transition process after slaughter of the animals without an impact on the muscle quality. The activities of the GP, PFK, CS, and complex I reflect the differences of the muscle fiber composition between the Pi and Du pigs.