Muscular Partitioning in the Semitendinosus Muscle of the Pig Compartimientos Musculares del Músculo Semitendinoso del Cerdo

SUMMARY: Neuromuscular compartments are subvolumens supplied by a primary nerve branch with homogeneous fiber characteristics. This muscular organization is important for understanding the muscle function in relation to postural and dynamic implications and also is relevant for appraising meat quality. Current researches associate fiber muscle characteristics with perimortem processes that regulate muscle transformation into meat. It is known that pig muscle has four heavy chain myosin isoforms: I, IIa, IIx and IIb. Castrated male pigs were slaughtered at 100 kg live weight. Semitendinosus muscle samples of each subvolumen determined previously (R1, R2, R3, R4) were frozen in liquid nitrogen and reacted for myofibrillar ATPase and NADH-TR for determining fiber types and oxidative capacity respectively. It were identified I, IIA and IIX/IIB fiber types. The frequency distribution of the I, IIA, and IIX/IIB fiber types were significantly greater in R1- R4, R4 and R3 respectively. The CSA of all fiber types was significantly larger in R1 than other compartments, notwithstanding CSA did not vary significantly among fiber types; oxidative capacity was significantly greater in R4. These results show a heterogeneousness of the muscle which would explain probably the disagreements documented between characteristics of fiber and meat quality traits.