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Salmonella surrogate mitigation in poultry feed using a dry acid powder
Salmonella contamination is a prevalent concern for the feed industry. Heat treatment is commonly used to mitigate pathogens, but it is a point-in-time strategy that does not prevent recontamination. Chemical alternatives may limit recontamination, but are often difficult to mix effectively or corrode equipment. A dry acid powder, such as sodium bisulfate (SBS; Jones-Hamilton, Co., Waldridge, OH), may be a practical option for pathogen mitigation. Therefore, the objective of this experiment was to evaluate the effectiveness of SBS to mitigate post-processing contamination of a Salmonella surrogate, Enterococcus faecium (E. faecium) ATCC 8459, in poultry feeds. Treatments were arranged in a 2 × 6 factorial with two feed forms (non-processed mash vs pelleted feed) and 6 levels of SBS (0, 0.175, 0.35, 0.70, 1.4, and 2.8% w/w). A standard, broiler grower feed was inoculated with E. faecium, treatments mixed with SBS, and pelleted at 70°C on a pilot-scale California Pellet Mill. Pellet production test was the experimental unit and there were three pellet production replicates. Treatments were randomized prior to pelleting and a non-inoculated flush was utilized between each treatment to prevent crossover contamination. Mash samples before thermal processing and corresponding pelleted samples were collected. Samples were analyzed for E. faecium on d 0, 2, 4, 7, and 14. All main effects and interactions were significant (P < 0.0001). Specifically, pelleting resulted in a 3-log reduction in E. faecium (P < 0.0001; 6.6×10^5 vs. 2.3×10^2 CFU/g for mash vs. pelleted, respectively). In both pelleted and mash feeds, there was a linear decline in E. faecium with increasing SBS inclusion (P < 0.0001; 1.3×10^4, 9.8×10^3, 8.5×10^3, 7.7×10^3, 7.6×10^3, 2.5×10^3 CFU/g for 0, 0.175, 0.35, 0.70, 1.4, and 2.8% SBS, respectively for mash feeds on d 14). There was also a linear decrease in E. faecium over time (P < 0.0001, 6.7×10^5, 6.9×10^4, 6.0×10^4, 5.0×10^3, and 1.3×10^3 CFU/g for the negative control on d 0, 2, 4, 7, and 14, respectively). In summary, this research suggests that thermal processing, time, and SBS concentration all impact pathogen levels in poultry feeds, and that including a dry acid powder may be an effective pathogen mitigation strategy.
Keywords: Salmonella, feed safety, pathogen, Enterococcus faecium, poultry, sodium bisulfate