Integrated risk evaluation of in- and outputs, including heavy metals, in broiler farm environments for the appearance of antimicrobial resistance

Although recommendations for nutritional factors have already been studied, derived and published, nutrients like trace elements continue to be much higher supplemented in broiler feed than required. If these nutrients, such as heavy metals as trace elements, are excreted due to an oversupply, they might accumulate in the environment and cause a major impact due to the risk of antibiotic-resistant co-selection. The aim of this study was to evaluate the accumulation of these nutritional factors in environmental samples, and their influential risk for the occurrence of antibiotic-resistant opportunistic pathogens. Samples from fresh feed and bedding, water from the water line, and manure and dust from broiler houses were collected during the last week of the fattening period from 14 German broiler farms. The pH of water, feed, bedding and manure, the water turbidity and electric conductivity, and nutritional (crude ash (CA), crude protein (CP), metabolic nitrogen (N_met), crude fat), and fiber components (neutral detergent fiber, acid detergent fiber, acid detergent lignin) from feed, bedding and manure, as well as elements (n = 31) from all 5 sample types were analyzed. Additionally, the water, manure and dust were tested for the occurrence of methicillin-resistant Staphylococcus aureus and species with resistance to extended-spectrum beta-lactams. Group differences of the chemical analyses between the sample types and the risk of antibiotic-resistant, opportunistic microorganisms was evaluated. An accumulation of moisture, CA and CP could be observed from the feed and bedding to the manure samples, and in elements, from feed, bedding and water to manure and dust. The risk evaluation indicated a lower risk of antibiotic-resistant, opportunistic pathogens with higher concentrations of fiber in bedding or manure, and a higher risk with higher relative amounts of N_met in manure. Therefore, especially high fiber in bedding and low CP in feed could be relevant parameters for improving the health status of broilers, and N_met in manure could serve as a parameter for evaluating the environmental impact.