Animal poo may make food safer

A new study suggests that animal manure (poo) may be a safer bet than conventional fertilisers in protecting the public from food-borne diseases – provided the manure is treated appropriately.

A new analysis of a 27-year experiment comparing organic and conventional soil management indicates that animal-based composts do not promote pathogen survival and may even promote bacterial communities that suppress pathogens. Credit: Dr. Devarajan

Prevailing attitudes in microbial research see animal manure as a danger to public health, and for valid reasons. Notable disease-causing bacteria are associated with animal manure, including E. coli, Salmonella, and Giardia.

But the research, published today in the Journal of Applied Microbiology, suggests that when used safely, animal manure does not promote pathogen survival and may even encourage the growth of bacterial communities that suppress pathogens.

“Our findings suggest that abandoning animal-based composts should be reconsidered, both because of the known benefits of composts for soil health and because it may be possible to apply amendments so that food-safety risks are mitigated rather than exacerbated,” says lead author Naresh Devarajan, from the University of California, Davis, in the US.

The results come from a longitudinal, 27-year study comparing organic and conventional (i.e. chemical-based) fertilisers.

Safe methods for preparing animal manure may include composting and drying the manure, longer storage periods, or specific treatments for stabilisation, as well as taking steps to ensure clean, non-stressful environments for livestock, according to a number of recent studies.

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