Location: Meats Safety & Quality Research2012 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.
3. Progress Report:
Reducing pathogen shedding by cattle will require identification of the ecological and environmental factors that affect pathogen occurrence and persistence in the animal. In 2012, we completed studies to determine if switching diets to predominantly corn can reduce the load of E. coli O157:H7 in cattle that were fed high levels of wet distillers grains. We continued 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 continued 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 is critical for developing intervention strategies to reduce this pathogen in cattle. Developing effective strategies to reduce pathogens in cattle also will require the understanding of factors that affect pathogen occurrence and transmission in the production environment. There is increasing interest in the use 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 FY 2012, we completed studies to evaluate the influence 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. In addition, we initiated studies to confirm a role for environmental persistence of E. coli O157:H7 in feedlot surface manure in the persistence and transmission of this pathogen in cattle. Airborne transport of E. coli O157:H7 is a potential mode of transmission of this pathogen among cattle in the production environment, as well as to the environments surrounding cattle production facilities. We continued studies to determine if E. coli O157:H7 can be transported in windborne bioaerosols from cattle feedlots. In 2012, we examined production factors impacting pathogens in swine, as well as intervention strategies to reduce pathogens in swine. Studies were completed to determine if age of piglets at weaning affects pathogen shedding in swine fed antibiotic-free diets. In addition, studies with 21-day-old nursery piglets were completed, 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.
1. Natural antimicrobials to replace antibiotics in swine diets. Young swine often are fed dietary antibiotics to improve health, reduce pathogen load, and enhance performance. However, few natural alternatives have been identified to replace these compounds in the diet if swine producers are required to eliminate antibiotic use. Lysozyme is a naturally occurring enzyme produced by animals to combat microbial colonization. ARS scientists at Clay Center, NE, determined that a commercial product containing lysozyme could replace dietary antibiotics in 10-day old early-weaned piglets. Dietary lysozyme reduced Campylobacter coli and Shigatoxin genes in feces of piglets, compared to diets without supplemented antibiotics. Lysozyme and antibiotic treatments had similar effects on pathogen load. Use of lysozyme in diets of young piglets could maintain a safe food supply and reduce the use of prophylactic antibiotics that are typically used for swine production.
Wells, J., Shackelford, S.D., Berry, E.D., Kalchayanand, N., Bosilevac, J.M., Wheeler, T.L. 2011. Impact of reducing the level of wet distillers grains fed to cattle prior to harvest on prevalence and levels of Escherichia coli O157:H7 in feces and on hides. Journal of Food Protection. 74(10):1611-1617.