Ability of unsterilized recycled manure solids bedding to support growth of Klebsiella pneumoniae and Escherichia coli

Although recycled manure solids (RMS) bedding is used on dairy farms, it could allow bacterial growth when contaminated by feces and thus increase the incidence of clinical mastitis in cows. The objective of this study was to describe bacterial growth in three different types of RMS bedding, as well as in sand, when samples were experimentally inoculated with Escherichia coli and Klebsiella pneumoniae. Two 3-day trials were conducted, during which treatments included inoculating bedding samples with E. coli and K. pneumoniae, as well as no inoculation. The trial was repeated 3 times for each bedding sample on each day. Samples were incubated at 15 degrees C for 3 d and bacterial counts were measured every day. After inoculation, there was no significant K. pneumoniae or E. coli growth phase during the trial in those RMS samples that were prepared either in a container or in a heap. Recycled manure solids and sand samples prepared in a rotary drum, however, showed a similar active growth phase of K. pneumoniae during the first 24 h of the trial. Moreover, a significant E. coli growth phase was observed in the samples of sand bedding in the first 24 h. The 3 different types of RMS bedding samples did not react in a similar manner to coliform inoculation. No active growth phase was observed in bedding samples already containing a high bacterial concentration following inoculation with coliforms.