A multi-strain, biofilm-forming cocktail of <i>Bacillus</i> spp. and <i>Pediococcus</i> spp. alters the microbial composition on polyethylene calf housing surfaces

Application of a beneficial microbial cocktail of <i>Bacillus</i> spp. and <i>Pediococcus</i> spp. was evaluated first for adherence to polyethylene calf hutch material, and second, to determine if application <i>in situ</i> to individual calf hutches post-cleaning influenced surface recolonization by enteric pathogens. Three treatments were utilized: (i) no application (<b>NC</b>), (ii) chlorine-free, distilled water (<b>DW</b>), or (iii) an application of a microbial inoculant containing <i>Bacillus</i> spp. and <i>Pediococcus</i> spp. at a concentration of 0.4 g/m² of hutch space (<b>LF</b>). Thirty-six 15 × 15 cm pieces of naïve, sterile polyethylene calf hutch material received either NC or LF and were incubated at 28°C, and bacterial growth was evaluated by total aerobic plate counts at 24, 48, and 72 h post-application. Thirty polyethylene calf hutches (<i>n</i> = 10/treatment) were randomized to NC, DW, or LF 24 h after cleaning. Calves were placed in the hutches 24 h after treatment application and monitored daily for 28 d. <i>In situ</i> surface samples were randomized by time from five unique locations within the calf hutch interior: 24 h post-cleaning and then 24 h, 7 d, 14 d, and 21 d post-application. Total aerobic plate counts and culture-independent approaches RT-qPCR and 16S amplicon sequencing were used to detect and identify the composition of the bacterial community <i>in situ</i>. The bacteria in the inoculant were able to successfully colonize on polyethylene, and application to individual polyethylene calf housing <i>in situ</i> influenced microbial diversity and reduced the presence of some undesirable bacteria on high-contact interior surfaces.IMPORTANCEDue to its multifactorial nature, neonatal calf diarrhea can be difficult to manage on farms. Clean housing environments are a critical disease control point, especially for calves less than one month of age. Application of a beneficial biofilm-forming bacterial product after cleaning of neonatal calf housing may influence the microbial communities present on the surface, particularly those that may present disease risk to calves in early life.