Buffering Capacity Comparison of Tris Phosphate Carbonate and Buffered Peptone Water Salmonella Pre-Enrichments for Manufactured Feed and Feed Ingredients

SIMPLE SUMMARY: This study compared two pre-enrichment mediums, tris phosphate carbonate (TPC) and buffered peptone water (BPW), for detecting Salmonella in animal feed. Samples (269) were collected from different feed mills and assessed for pH changes after a 24 h incubation. Different feed ingredients showed varying initial and final pH values. Meat and bone meal had higher final pH values in both TPC and BPW, while soybean and peanut meal had lower final pH values. BPW was more effective at recovering Salmonella and showed greater pH changes. Four Salmonella isolates were recovered from meat and bone meal samples, with BPW identifying more isolates. Overall, the study highlights the importance of choosing the right pre-enrichment medium for accurate Salmonella detection in animal feed. ABSTRACT: Various culture-based methods to detect Salmonella in animal feed have been developed due to the impact of this bacterium on public and animal health. For this project, tris phosphate carbonate (TPC) and buffered peptone water (BPW) buffering capacities were compared as pre-enrichment mediums for the detection of Salmonella in feed ingredients. A total of 269 samples were collected from 6 feed mills and mixed with the pre-enrichments; pH was measured before and after a 24 h incubation. Differences were observed when comparing pH values by sample type; DDGS and poultry by-product meal presented lower initial pH values for TPC and BPW compared to the other samples. For both TPC and BPW, meat and bone meal presented higher final pH values, while soybean meal and peanut meal had lower final pH values. Furthermore, for BPW, post cooling, pellet loadout, and wheat middlings reported lower final pH values. Additionally, most feed ingredients presented significant differences in pH change after 24 h of incubation, except DDGS. From meat and bone meal samples, four Salmonella isolates were recovered and identified: three using BPW and one using TPC. TPC provided greater buffer capacity towards neutral pH compared to BPW, but BPW was more effective at recovering Salmonella.