Effect of dietary protein level and fasting length on enzymatic activity of cathepsin B in live muscle and in meat from heavy finishing pigs

To evaluate the effect of dietary protein level (13.0% and 9.5% CP) and duration of fasting on the enzymatic activity of cathepsin B in live muscle and pig, 44 fattening pigs weighing 138 ± 9 kg were reared to slaughter (171 ± 9 kg). The feed allowance was set at 3.2 kg/day. Two weeks prior to slaughter, subjects on each diet were randomly assigned to one of two different fasting treatments (no fasting or 48 h fasting). After this treatment, an individual longissimus dorsi (LD) muscle sample was taken from each pig by biopsy at the level of the third lumbar vertebra and frozen in liquid nitrogen until analysis. Then, the subjects within each diet × fasting interaction were assigned to different fasting times before slaughter (4 or 28 or 52 h). One day after slaughter, LD and semimembranous muscle (SM) samples were taken from each carcass, kept at 4 °C for 24 h and then frozen in liquid nitrogen. The activity of cathepsin B was measured in muscle homogenates by colorimetric method. Dietary CP did not affect cathepsin activity in LD obtained in vivo and daily live weight gain up to slaughter. Compared to the absence of fasting, a cathepsin activity greater than 18% in LD was observed after 48 h of fasting (P < 0.01). Cathepsin activity in LD and SM sampled after slaughter was not affected by dietary protein level and fasting 2 weeks prior to slaughter. Compared with 28 h fasting, feeding exclusion for 52 h prior to slaughter increased cathepsin activity in the LD and SM muscles by 18% (P < 0.05) and 12% (P = 0.07) respectively. The preslaughter fasting length had no effect on fresh meat quality parameters (pH at 1 and 24 h post mortem, colour, drip losses, cooking losses).