Chemical Treatment to Remove or Prevent Salmonella Contamination of Poultry Feed

Introduction: Salmonella may contaminate livestock feed at several stages of production, transport and storage. Formaldehyde is an effective anti-Salmonella feed treatment, but it is now banned for this use in Europe. Organic acid-based additives are an alternative. Gap Statement: The efficacy of organic acid feed additives against natural Salmonella feed contamination is uncertain due to a paucity of reported work investigating low levels of infection that may be relevant for real-world situations. Aim: To compare the anti-Salmonella effects of feed additives based on formaldehyde versus those based on organic acids. Methodology: Experimental contamination of poultry feed with one of three Salmonella serovars at moderate (between 10 and 200 CFU/g) or low (around 1 CFU/g) levels was preceded (‘prevention’ mode) or followed (‘decontamination’ mode) by application of commercial antimicrobial additives. Storage at room temperature for 24 h was followed by pre-enrichment then culture. Results: Organic acid-based products at recommended application rates only eliminated detectable Salmonella from samples with the lowest degree of contamination. The effect was partial, with a proportion of samples still yielding Salmonella in most experiments, and only one such product showed efficacy above 50% of samples for the decontamination mode. The two formaldehyde-based products showed partial efficacy against moderate contamination, and one was entirely effective against low-level contamination even at its lower inclusion rate. Conclusions: Organic acid-based feed additives have a lesser anti-Salmonella effect than formaldehyde-based products at their respective recommended inclusion rates. However, some non-formaldehyde products may be substantially effective against a low, natural degree of contamination. Impact Statement: Chemical suppression of Salmonella in animal feed is an important element of measures to safeguard livestock health and, consequentially, public health too. The European ban on using formaldehyde for this purpose has necessitated the use of alternative products. The present work includes very low levels of Salmonella in feed, possibly mimicking natural contamination, to show that under these circumstances some such alternatives may be as efficacious as formaldehyde products.