2011 Annual Report
1a.Objectives (from AD-416)
Objective: 1. Identify the ecological and environmental factors, as well as critical points, that affect pathogen occurrence, survival, fate, and transport in cattle and swine production facilities, manure, and surrounding environments.
Objective 2. Develop and evaluate intervention strategies that reduce or eliminate the occurrence, persistence, or movement of foodborne pathogens among food animals, their environment, and potential surrounding production environments.
1b.Approach (from AD-416)
The overall goal of this project is to reduce the risk of human foodborne illness, by providing scientific information that can be used to reduce or eliminate the transmission of zoonotic pathogens from animal manure to food, water, and the environment. Primary targets of the work include pathogenic strains of Escherichia coli (including non-O157 Shiga-toxigenic E. coli), Salmonella spp., and Campylobacter spp. in cattle and swine. Approaches for reducing these pathogens include the reduction of pathogen colonization and shedding by livestock, as well as the reduction of pathogens shed and present in the manure and production environment. Exploitable factors, including biological, environmental, and managerial factors, which affect the occurrence, survival, or transmission of pathogens in cattle and/or swine manure will be identified, then manipulated and evaluated to determine the impact on pathogens. Strategies and interventions to reduce the dissemination of foodborne pathogens in cattle and swine manure or production environments will be developed and evaluated. Approaches will include the use of dietary amendments, manure additives, and waste management systems, as well as other intervention strategies that may be suggested by information gathered in experiments. Approaches that are both effective at reducing foodborne pathogens and environmentally safe under animal production practices will be identified. Expected outcomes are scientific information and procedures that will be used to reduce or eliminate zoonotic foodborne pathogens both in livestock and their manure, thus contributing to a safer food and water supply and a lower risk of human foodborne illness.
Feedlot diets with high levels of distillers grains can increase the prevalence of E. coli O157:H7 shedding by cattle. In 2011, we completed and analyzed studies to determine if high levels of wet distillers grains in cattle diets result in increased pathogen load on cattle in summer months when E. coli O157:H7 prevalence is typically high, and to determine if switching diets to predominantly corn can reduce the pathogen load. We also conducted studies to determine if cattle shedding E. coli O157:H7 in feces at high numbers, compared to animals that are consistently negative for the pathogen, are associated with specific differences in the gastrointestinal microflora, specific host genomic factors, immune response, and/or host behaviors, such as temperament, and eating or drinking habits. In addition, we initiated studies to identify specific bovine gastrointestinal tract locations that may have an important role in sustaining high levels of colonization and shedding of E. coli O157:H7 in feces. Understanding how these various factors impact E. coli O157:H7 in cattle and the production environment is critical for developing approaches for reducing this pathogen in cattle.
Studies were initiated to determine if age of piglet at weaning affects pathogen shedding in swine fed antibiotic-free diets. In addition, studies with 10-day-old early-weaned piglets were completed and studies with 21-day-old nursery piglets were initiated, to determine the impacts of diets containing the natural antimicrobial lysozyme on production performance and fecal shedding of the pathogens Salmonella, Campylobacter, and/or Shiga-toxin producing E. coli, compared to diets with and without dietary antibiotic growth promoters.
There is increasing interest in the construction of deep-bedded confinement facilities in the cattle feeding industry for a variety of reasons, including ease of manure management and improved cattle performance compared to open lot feedlots. In FY2011, we continued studies to evaluate the influence of a variety of different bedding materials on the populations of E. coli in deep-bedded cattle waste, in order to identify bedding materials that may limit the growth and persistence of these bacteria. The work is part of a larger collaborative effort that is also seeking to quantify and characterize odor emissions from cattle deep-bedded barns, with the goal to develop recommendations for managing these facilities to reduce odor, gas emissions, and pathogens.
Reducing the foodborne pathogen E. coli O157:H7 in cattle fed wet distillers grains. Wet distillers grains with solubles are a by-product of ethanol production commonly fed to cattle and previous data indicate that feeding high levels of wet distillers grains to feedlot cattle can increase the levels of E. coli O157:H7 in their feces compared to corn diets. ARS scientists at Clay Center, NE, investigated if shifting from higher to lower levels of wet distillers grains in the feedlot finishing diet would reduce the levels and frequency of E. coli O157:H7. In animals fed 40 or 70% wet distillers grains and switched to 0 or 15% wet distillers grains, E. coli O157:H7 frequency and levels in feces were lower compared to those in animals continuously fed 40% wet distillers grains. By day 56 after the switch, E. coli O157:H7 frequency and levels in feces were similar to that of animals fed 0% corn. Because feeding wet distillers grains is more economical than corn for beef producers, switching finishing cattle from high levels of wet distillers grains in the diet to 15% or less at least 56 days prior to harvest may be a viable option for minimizing consumer food safety risks attributable to E. coli O157:H7 while retaining the advantages of feeding wet distiller grains.