Submitted to: Journal of Applied Poultry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 16, 2000
Publication Date: January 1, 2001
Citation: BUHR, R.J., DICKENS, J.A. CROP EXTRACTION FORCE AND EFFICIENCY OF CROP REMOVAL DURING MANUAL EVISCERATION OF BROILERS:1. EVALUATION OF STUNNING VOLTAGE AND METHOD OF BLEEDING. JOURNAL OF APPLIED POULTRY RESEARCH. 2001. Interpretive Summary: Removal of the digestive system intact from poultry carcasses is the basic goal of evisceration. Incomplete removal or rupture during can potentially lead to bacterial contamination. Chickens store feed awaiting digestion in a pouch of the esophagus, the crop, located at the base of the neck. Removing the crop completely during evisceration occurs only 75% of the time. Electrical stunning is used to render poultry unconscious and the influence on crop removal is not known. Electrical current applied to the carcass induces muscles to contract and swelling after death, and may restrict the opening into the chest and prevent the passage of the crop during evisceration. The objectives of this study were to evaluate electrical stunning (12, 50, or 200 V) on the incidence of crops removed intact and the force recorded. Stunning voltages did not influence crop pull force (3.5 kg at 6 wks and 4.4 kg at 7 wks). However, the incidence of crops removed intact at 7 wks was higher for those stunned at 12 V (84%) than for those stunned at 50 and 200 V (62%). This difference in the incidence of crops removed intact was not observed when repeated with broilers at 6 wks of age that were stunned at 12 and 50 V (76%). Less force was required to extract intact crops than to extract crops that ruptured during evisceration.
Technical Abstract: Attention has been refocused on the mechanics of crop removal in order to minimize crop breakage and leakage of contents, potentially contaminating the carcass with bacteria pathogenic to humans. A series of experiments was conducted to evaluate the influence of stunning voltage and bleeding conditions on the incidence of intact crop removal and the peak pull force recorded during manual evisceration of male broilers. Stunning voltages of 12, 50, or 200 V, or 12 V followed by post-kill stunning, were applied at 6 or 7 wk of age. Carcass positioning for automated and manual bleeding, in addition to head removal prior to or during picking, was also evaluated. Stunning voltages did not influence the peak pull force required to remove the crop intact (3.47 to 3.50 kg at 6 wk and 4.14 to 4.64 kg at 7 wk). However, the incidence of crops removed intact at 7 wk was higher for those stunned at 12 V and 12 V plus post-kill stunning (84%) than for those stunned at 50 and 200 V (62%). This difference in the incidence of crops removed intact was not observed when repeated with broilers at 6 wk of age that were stunned at 12 and 50 V (76%). Automated head positioning for bleeding, or head removal prior to or during picking did not alter the incidence in intact crop removal (76 and 80% respectively, when stunned at 12 V). Less force was required to extract intact crops than to extract crops that ruptured during evisceration. These results further support previous observations that the crop appears to rupture during evisceration not due to weakness, but due to greater adhesion.