In response to reports that the contamination of food can occur during the on-farm primary phase of food
production, we report data that describes a possible cost-effective intervention measure. The effect of time
before soil incorporation of livestock wastes spread to land on the rate of decline of zoonotic agents present in
the waste was investigated. Fresh livestock wastes were inoculated with laboratory-cultured Salmonella, Listeria,
and Campylobacter spp. and Escherichia coli O157 before they were spead onto soil. Incorporation of the spread
wastes was either immediate, delayed for 1 week, or did not occur at all. Bacterial decline was monitored over
time and found to be significantly more rapid for all waste types when they were left on the soil surface. There
were no significant differences in initial bacterial decline rates when wastes were spread in summer or winter.
Our results indicate that not incorporating contaminated livestock wastes into soil is a potential intervention
measure that may help to limit the spread of zoonotic agents further up the food chain. The implications of
these findings are discussed in relation to current advice for livestock waste disposal.