Adenine nucleotide concentrations and glycolytic enzyme activities in longissimus muscle samples of different pig genotypes collected before and after slaughter.

Longissimus muscle samples from the pig genotypes Duroc (Du), Pietrain (MHS homozygote negative (PiNN), positive (PiPP)) and a Duroc-Pietrain crossbreed (DuPi) were analyzed. The PiPP samples showed a faster pH drop and higher electrical conductivity, drip loss and lightness values. Before slaughter the concentrations of the adenine nucleotides were comparable between the genotypes, but 40 min after slaughter (p.m.) the ATP concentrations decreased and IMP increased, to a higher extent in the PiPP pigs. The nucleotide values of the 12 h p.m. samples were again comparable. Activities of glycogen phosporylase (GP), phosphofructokinase (PFK) and lactate dehydrogenase (LDH) were nearly similar before slaughter. Forty minutes after slaughter the LDH activities increased in all pigs and the PFK activities in all genotypes but not in the PiPP. GP results were rather inconsistent indicating an earlier activation of this enzyme. The study showed that the reduced meat quality in the PiPP pigs is accompanied with rapid ATP degradation and accelerated enzyme activation.

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 crossbreed.

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.

Mitochondrial respiratory activity in porcine longissimus muscle fibers of different pig genetics in relation to their meat quality.

The pig genetics of Duroc, Pietrain (MHS homozygote negative, PiNN), Pietrain (MHS homozygote positive, PiPP) and a F2-Duroc-Pietrain cross-breed were analyzed. The animals had comparable (P>0.05) carcass weights, but the PiPP pigs had higher carcass yield and lean meat values (P<0.05). Considering the meat quality characteristics, the PiPP showed a faster pH drop and higher electrical conductivity, drip loss, shear force as well as lightness and redness values (P<0.05). The PiPP animals had less slow-twitch-oxidative (STO) and more fast-twitch-glycolytic (FTG) muscle fibers, whereas the results of the Duroc animals were converse (P<0.05). The STO and FTG fibers of the PiPP animals were larger than those of the other genetics (P<0.05). The analysis of the mitochondrial respiratory activity (MRA) using permeabilized longissimus muscle fibers resulted in no differences between the pig genetics before and immediately after slaughter. During chilling the MRA decreased in all pigs but to a higher extent in the PiPP pigs (P<0.05).

Developmental programming of skeletal muscle phenotype/metabolism.

Skeletal muscle is a highly dynamic and malleable tissue that is able to adapt to different stimuli placed upon it, both during gestation and after birth, ultimately resulting in anatomical changes to muscle fibre composition. Variation in nutrient supply throughout gestation is common, whether in livestock or in the human. The specific effects of maternal nutrition on foetal development are at the forefront of scientific research. However, results describing how different maternal feeding strategies affect skeletal muscle fibre development in the offspring are not fully consistent, even where the same time windows during gestation have been examined. The aim of this study is to determine the effects of increased maternal nutrition (above the recommended levels) on the Musculus semitendinosus phenotype of progeny. In all, 24 pregnant sows were assigned to one of four feeding regimes during gestation; T1 (control group): 30 MJ digestible energy per day (MJ DE/day) throughout gestation, T2: same as that for T1 but increased to 60 MJ DE/day from 25 to 50 days of gestation (dg), T3: same as that for T1 but increased to 60 MJ DE/day from 50 to 80 dg, T4: same as that for T1 but increased nutrition to 60 MJ DE/day from 25 to 80 dg. Light- and heavy-weight littermate pairs of the same sex were selected at birth and individually fed to slaughter (c. 158 days). Histochemical and immunohistochemical staining were used to identify the predominantly oxidative (deep) and less oxidative (superficial) regions of the M. semitendinosus, and to determine total fibre number and proportions of fibre types. The results demonstrate that increased maternal nutrition alters skeletal muscle phenotype in the offspring by changing fibre-type proportions, leading to an increased oxidative capacity due to an increase in Type IIA fibres. No change in total muscle area, total muscle fibre number, or fibre cross-sectional area is observed. The precise molecular mechanism(s) by which these findings occur is being investigated.