Survival of pathogenic indicator organisms in stored swine manure containing ground piglet carcasses during cold temperatures

Blending homogenized swine carcasses with liquid swine manure raises concerns of pathogen survival in liquid manure that could pose a public and/or animal health hazard. The research objective was to determine the effects of cold temperature on the survival of selected pathogenic indicator organisms in liquid/frozen manure/carcass mixtures. Piglet carcasses were homogenized and inoculated with T₁ coliphage and Salmonella anatum. This mixture of carcass and pathogenic indicator organisms was added to liquid manure to represent 0, 2, 4, or 6% of the total dry matter. Liquid manure after inoculation was stored outdoors in Minnesota from 22 January through 29 June. Detectable levels of T₁ coliphage were present in samples collected 81 days after inoculation for the 2, 4, and 6% treatments. However, coliphage levels returned to those of the control treatment by Day 95 for all treatments. Fifty percent of the samples were positive for S. anatum on Day 95 for the 2 and 4% treatments while 100% of samples collected from the 6% treatment were positive for S. anatum. By Day 109, S. anatum could not be detected in any samples. T₁ coliphage and S. anatum can survive in liquid swine manure containing ground piglet carcass for up to 95 and 109 days, respectively when stored in cold environmental temperatures (<10°C). The ability of these organisms to overwinter suggests that soil could become infected with pathogens when slurry is applied to cropland in the spring. Once the manure temperature exceeded 15°C, the die-off rates dramatically increased. It is clear that the pathogenic indicator organisms in this study survived over winter. Presumably, other pathogenic organisms could also overwinter in liquid manure containing ground piglet carcass. The ability of these pathogens that overwinter in manure to cause infection in target species is presently unclear.