Effect of electrical stunning amperage and peri-mortem struggle on broiler breast rigor development and meat quality

Two experiments were conducted to determine the effects of electrical stunning and peri-mortem muscle activity (struggle in and around the time of slaughter) on post-mortem biochemical reactions in broiler breast muscle (Pectoralis major). Broilers were stunned with either 50 or 125 mA or were killed without stunning. In Experiment 1 (n = 273), broilers were either physically restrained to reduce struggling during slaughter or were unrestrained and allowed to struggle freely. Breast mean pH and R-value (ratio of adenosine to inosine nucleotides) were determined at 15 min and 24 h post-mortem, and Allo-Kramer shear was determined on 48 h post-mortem cooked meat samples from muscles excised at 15 min or 24 h. In Experiment 2 (n = 65), the breast muscle was unilaterally denervated by surgically severing the Pectoralis nerve on one side and performing a sham operation on the contralateral side. Results indicated that physical restraint resulted in higher muscle pH and lower R-values at 15 min post-mortem in the unstunned birds and birds stunned at 50 mA, but had no effect on breast meat from birds stunned at 125 mA. There were no treatment effects on meat tenderness or 24-h post-mortem pH or R-values. Stunning amperage had no effect on denervated muscle pH at 15 min post-mortem, but did affect the sham-operated muscle pH and R-values as in Experiment 1. These results indicate that the main effect of electrical stunning on early rigor development may be due primarily to inhibition of peri-mortem struggle.