Submitted to: Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/23/2005
Publication Date: 11/1/2005
Citation: Buhr, R.J., Berrang, M.E., Cason Jr, J.A., Bourassa, D.V. 2005. Recovery of bacteria from broiler carcass respiratory tracts before and after immersion scalding. Poultry Science. 84(11):1769-1773. Interpretive Summary: During slaughter, immersion scalding lowers external broiler carcass bacterial numbers, but scalding also results in a small increase in the number of bacteria recovered from the respiratory tract. Two experiments were conducted to determine if closing off the trachea (windpipe) in experiment 1, or cutting of the head in experiment 2, during bleed-out could minimize respiratory tract contamination during immersion scalding. Following stunning and initiation of bleeding, carcasses were either removed, had a plastic cable-tie applied around the neck and tightened to close off the trachea, or had heads removed. After commercial scalding, carcasses were again collected for sampling. In both experiments, a respiratory tract rinse was collected. Results confirmed that bacteria numbers increased within the respiratory tract during immersion scalding when the conventional bleeding method was used. This increase was prevented by blocking the trachea off just prior to scalding. Head removal did not alter the number of bacteria recovered prior to or following immersion scalding. This suggests that the rate of the onset of death was similar in both conventional bled and head-removed carcasses. The rate of the onset of death during bleeding may be the major factor in determining the level of bacterial contamination that occurs during immersion scalding. Removing the heads from bled carcasses prior to scalding would eliminate any possibility of slaughtered poultry regaining consciousness but would not change the number of bacteria entering the respiratory tract.
Technical Abstract: Occluding the trachea and decapitation were compared with conventional unilateral neck cut for effects on entry of bacteria into the respiratory tract of broilers during scalding. In experiment 1, the trachea was occluded prior to the broiler carcass entering the scalder, to determine if the bacterial recovery from the respiratory tracts could be diminished. The first carcass was removed at the end of bleed-out and a plastic cable-tie was placed around the neck of a second carcass and tightened to occlude the trachea. After proceeding through the triple-tank scalder the second carcass (trachea occluded) was removed, and then a third carcass (which did not have the trachea occluded during scalding) was removed. In the second experiment, carcasses were either unilaterally bled or decapitated. Unilaterally bled and decapitated carcasses were removed at both the end of bleed-out and following scalding. In both experiments, the trachea was cannulated and a respiratory tract rinse collected. For experiment 1, the numbers of bacteria recovered (log10 cfu/mL of rinse) from prescald, non-occluded carcasses were 2.5 E. coli, 2.6 coliforms, and 3.2 total aerobic bacteria. Rinses from carcasses sampled postscald (without occluding the trachea) had higher bacteria numbers at 4.6 E. coli, 5.0 coliforms, and 5.4 total aerobic bacteria. Carcasses that had the trachea occluded prior to entering the scalder had the lowest number of bacteria at 1.9 E. coli, 2.3 coliforms, and 2.7 total aerobic bacteria. In experiment 2, the numbers of bacteria recovered from unilaterally bled or decapitated carcasses did not differ prescald or post scald, although postscald values were significantly higher. Results confirmed that bacteria numbers increased within the respiratory tract during immersion scalding, the increase can be prevented by occluding the trachea prior to scalding, and decapitation did not alter the number of bacteria recovered prior to or following immersion scalding.