Horse manure needs to be ‘cooked’ for a specific length of time and at high enough temperatures to result in sufficient reductions in viability of roundworm (Parascaris equorum) eggs and Rhodococcus equi populations, report French researchers.

Composting, a popular method of managing horse manure generated on both small and large acreage farms, must be closely controlled to prevent environmental contamination, disease in foals and horses grazing treated pastures, and to minimize public health concerns.

It is known that the organism R. equi and P. equorum eggs are both very hardy and can, according to the French researchers, “remain infective for years on pastures and in compost.” Considering the danger of both R. equi and P. equorum eggs to horses and humans, the French research team, led by Laurent Hébert from Laboratoire d’Etudes et de Recherches en Pathologie Equine (AFSSA) in France, evaluated times and temperatures necessary to prevent environmental contamination with R. equi and P. equorum eggs.

Hébert and colleagues found that to reduce the number of live R. equi organisms below detectable levels, manure must be maintained at 45°C for 5.7 days, 50°C for 2.9 days, 55°C for 24 hours, and 60°C for 5.7 hours. In contrast, a substantial reduction in viability of P. equorum eggs can be achieved in less than two hours at 55°C and 60°C