This is a food safety issue. Raw manure has the potential to contain foodborne pathogens (microorganisms that cause human disease). Pathogens that live in the intestines of animals can be transmitted from their manure to produce in a number of ways and from there to people under certain conditions. For example, E. coli O157:H7 (a particularly dangerous pathogen) lives in the intestines of some cattle and Salmonella (consistently one of the top causes of foodborne illness worldwide) lives in the intestines of some poultry.
A 2015 FDA report on the assessment of the risk to public health from on-farm contamination of produce identifies BSAs of animal origin as a potentially significant source of pathogens.