Metabolic characteristics of semitendinosus and gluteus medius muscles in bullfighting bulls at enzymatic level

Muscle metabolic characteristics can be determined by the ratios between ke y enzymes of the main energy-supplying pathways. It was shown that enzyme g roups of constant proportions exit and represent no variable units within t he enzyme activity. This study was aimed at comparing the enzymatic level o f two bovine locomotor muscles. Biopsies were extracted from 24 male bullfi ghting bulls, aged between 4 and 5 years and belonging to four different Sp anish farms. Four samples were taken from each animal: 2 from the semitendi nosus muscle (ST) and 2 from the gluteus medius muscle (GM) at absolute dep ths of 30 and 50 mm. The activities of the enzymes CS (Krebs cycle oxidativ e potential), HAD (beta -oxidation), HK (glucose phosphorylation), PHOS (gl ycogenolysis) and LDH (glycolytic capacity) were analysed. The following en zyme ratios were considered: PHOS/LDH; HK/CS; HAD/CS; LDH/CS and PHOS/HK. S ome metabolic characteristics between both muscles and depths were found. N o significant differences were detected in the HK/CS ratio in the ST and in the GM, whereas the LDH/CS ratio was higher in the ST at 30 mm and in the GM at 50 mm. No differences were detected between both depths in the GM mus cle, for the HK/CS ratio and LDH/CS ratio. In contrast, in the ST muscle, t he LDH/CS and HK/CS ratios were statistically higher at 30 than at 50 mm de pth. The most evident differences were observed when the four farms were co mpared. This study showed that the main metabolic differences between the b ovine ST and GM muscles were the relationships between the capacities to us e extracellular energy sources, to oxidise Acetyl CoA in the Krebs cycle an d to reduce pyruvate to lactate.