Effect of fasting on energy metabolism and tenderizing enzymes in chicken breast muscle early postmortem

Pre-slaughter fasting is a very important practice in the meat industry. The present study was designed to investigate the effect of fasting on energy metabolism and tenderizing enzymes in chicken muscle early postmortem. A total of 30 Yellow-feathered chickens were deprived of feed for 0 h, 12 h and 24 h before slaughter (n = 10 each group). Breast muscles were removed and cut into 3 parts and stored at 0 °C for 0 h, 3 h and 10 h. Samples were used for analyses of zymography, cathepsins, pH, glycogen/ATP/ADP/AMP, hormones and ultrastructure. Fasting caused the accelerated depletion (p < 0.05) of glycogen, ATP and ADP before or immediately after slaughter, but no difference existed in ATP at 3 and 10 h (p > 0.05). Fasting resulted in greater ultimate pH (p < 0.05). Zymography indicated that fasting delayed the activation of μ/m-calpain (p < 0.05), however, it accelerated the release of lysosomal enzymes (p < 0.05). Fasting for 24 h resulted in greater ultrastructural changes and plasma corticosterone levels than fasting for 12 h and control groups. Therefore, fasting for no more than 12 h is acceptable in practice.