A group of researchers from the Georgia Tech Research Institute, University of Saskatchewan, University of Georgia, Auburn University, USDA-ARS U.S National Poultry Research Center, and Tyson Foods studied the concept of an alternative slaughtering procedure on farm and its effects on carcass quality, carcass microbiology, and meat quality. The team hypothesized that the on-farm slaughter and transport system, or FSaT, may improve welfare and efficiency by decreasing handling and eradicating live transport, getting rid of dead-on-arrivals, reduce water, energy use, and labor, and be a more economically viable option. The proposed FSaT system would require two 53-foot trailers, one for processing and the other for actual transport to the processing plant. The proposed concept would have mechanical harvesting, loading, stunning, shackling, and bleeding on the mobile unit at the farm. Transport to the processing plant would follow.
To test the effects of delayed processing on defeathering, an experiment was conducted at a broiler processing facility. Three different trials were conducted on three different days and 80 carcasses were used in each trial. 60 were randomly chosen and removed from the shackle line before entering the scalder. They were assigned to 3 different groups which entailed either a 2, 4, or 6-hour delayed scalding and defeathering. The other 20 carcasses from each of the trials were allowed to pass normally through the scalding tanks and were defeathered as normal. They were used as a control group as New York Dressed carcasses. After the assigned time had passed, the 60 carcasses were rehung, scalded, and picked. The carcasses were graded on four characteristics that included feather picking quality, number of broken wings, number of broken shanks, and other carcass damage. The researchers found that delayed scalding did not directly impact feather retention force and that carcass stiffness most likely had an effect on rotation during defeathering and resulted in higher scores for all of the delayed groups.
To assess the effects of delayed processing on carcass microbiology, three experiments were conducted. In the first, carcasses were held for 0 or 8 hours after slaughter and eviscerated whole carcass rinses (WCR) were assessed for aerobic plate counts (APC), Enterobacteriaceae (EB), Salmonella, and Campylobacter. They found that for the carcasses that were held for 8 hours, APC, EB, Salmonella, and Campylobacter were higher. In the second experiment, carcasses were held for 0 or 4 hours at 4, 27 or 40 ֯C and eviscerated WCR was once again evaluated for the same factors. They found that there were less positive Salmonella samples in the carcasses held at 40C. They found no differences between the carcasses in APC, EB, or Campylobacter. The third experiment, carcasses were processed in a commercial broiler processing plant and held for either 0, 2, 4, or 6 hours. After the carcasses were defeathered, the carcass rinses were evaluated for the same factors. The team found no differences for EB and Salmonella, but there were increases in APC after the 4 or 6-hour holding period and increases in Campylobacter between 2 and 4 hours. They believe this may be due to processing happening later in the shift at the processing plant.
To evaluate the effects of delayed processing on breast meat quality, the researchers conducted two studies. The first assessed electrical, carbon dioxide gas, and low atmosphere hypoxia stunning methods and a delay of two hours between bleeding and scalding at a pilot processing plant. The second study assessed the effects of a 0, 2, 4, 6-hour delay between electrical stunning and bleeding, and scalding. Delayed processing in both of the studies resulted in red discoloration on the cranial end of the breast muscle. This discoloration was more common with the use of gas and atmosphere stunning in the pilot plant and with longer delays at the commercial plant. Delayed processing had minimal effects on water holding capacity. In the pilot plant study, muscle drip loss was increased in delayed samples after 4 and 7 days of cold storage. Cook loss was not impacted in the pilot plant study, but there were greater levels in the commercial plant study with the 6 hour delay. Cooked meat shear force decreased as delay time increased in the commercial plant study and lower values than controls were seen in the pilot plant study. There was a positive impact on marinade uptake in the commercial plant study and no impact in the pilot plant study.
What does this mean for producers?
- The proposed FSaT system may be a viable option for processing due to the lack of major differences between traditional and delayed processing on factors such as defeathering quality, carcass microbiology, and meat quality.
The full paper can be found in the December 2023 edition of Poultry Science and online here https://doi.org/10.1016/j.psj.2023.103137
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