Dietary Impact on Antibiotic Resistance in Feedlot Manure

There is a growing public concern regarding antibiotic resistance and the use of antibiotics, including in livestock management. Understanding the ecology of antibiotic resistance among microbes, identifying resistance gene reservoirs, and implementing antibiotic resistance mitigation practices in livestock production are critical to protecting animal and human health while meeting increasing food demands. This research is one of several studies seeking to assess risk for livestock- to- human transfer of antibiotic resistance and to identify mechanisms for reducing that risk where possible. This study evaluated the impact of forage concentration and supplemental essential oil in beef cattle finishing diets on antibiotic resistance in freshly excreted and consolidated beef feedlot manure. Results indicate that antibiotic resistance in manure was not impacted by either of the two dietary treatments considered

Antibiotic Resistance in Manure- Amended Agricultural Soils

Manure application to agricultural land benefits soil health and agronomic yields. However, as antibiotic resistance becomes a more serious threat to public health, there is concern that antibiotic resistance originating from livestock manure could impact human health through contamination of the environment or food. This study sought to quantify this risk by monitoring concentrations of antibiotic resistance bacteria and genes in fallow soil during the period of October through April, representing fall manure application through spring planting. Resistance to three common antibiotics— tylosin, azithromycin and tetracycline— was monitored following application of fresh, stockpiled, or composted beef feedlot manure, or inorganic fertilizer. Overall, concentrations of all monitored resistant bacteria were below the detection limit for enumeration. Results indicate that while all the manure treatments increased at least one measure of antibiotic resistance during the sampling period, by the final sampling day antibiotic resistance prevalence and concentrations in manured plots were not significantly different from soil receiving no fertilizer treatments