Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2016
Publication Date: N/A
Interpretive Summary: This study describes, for the first time, the establishment of bacterial pathogens and antibiotic resistant bacteria into a newly established broiler farm. A set of three broiler concentrated animal feeding operation houses were monitored from inception through 11 flocks, approximately 2 years’ worth of sample collection. From the first sample collection, 3 weeks into the first flock, Salmonella, Listeria, and antibiotic resistant bacteria had established and colonized the new litter. The influence of intra-house location was not as evident for most measured bacteria and antibiotic resistance; however, some pathogens and fecal indicator bacteria were more readily associated with the moist environments beneath the watering lines and near the outer wall. While a sharp increase in antibiotic resistant bacteria was noted within the first 3 weeks, there was no association with house location or side. Pre-flock litter and soil was devoid of most measured fecal bacterial indicators and pathogens; therefore, the study demonstrates the colonization event coincidental with chick introduction, rather than from the environment. Once colonization takes hold, typical cyclical microbial levels seen in other studies becomes normal. This is the first study of its kind demonstrating the evolution and eventual colonization of bacterial pathogens and antibiotic resistance within the broiler litter environment.
Technical Abstract: : Conventional commercial broiler production involves the rearing of more than 20,000 broilers in a single confined space, atop bedding material such as pine shavings or rice hulls, for approximately 6.5 weeks. This environment is known for harboring pathogens and antibiotic resistant bacteria, but studies have focused on previously established houses. A concerted effort by the broiler industry has involved the scaling back of antibiotic use on-farm, but this has only been a recent occurrence. In the current study, a set of three naïve houses were followed from inception through 11 broiler flocks and monitored for ambient climatic conditions, bacterial pathogens, and antibiotic resistance. Within the first 3 weeks of the first flock cycle, 100% of litter samples were positive for Salmonella and Listeria while Campylobacter was culture negative. In all likelihood, given that pre flock bedding and soil levels were negative for pathogens and 4-5 orders of magnitude lower for other indicators, chicks most likely provided the colonizing bacteria. The influence of intra-house location was minor with only watering lines and side walls influencing some pathogen and indicator levels. Most bacterial groups experienced the typical cyclical pattern of litter contamination seen in other studies. This study represents a first of its kind view into the time required for bacterial pathogens and antibiotic resistance to colonize and establish in naïve broiler houses.