Date Full Report Received


Date Abstract Report Received



Primary Investigator:

The objective of this study was to determine the effect of swine manure pit additives and disinfectants on the concentrations of swine manure constituents including nutrients, antibiotics and antibiotic resistance genes. Current swine industry practice is to house animals in confinement facilities which capture and store slurry in pits. Additives may be placed in swine manure pits to aid in solids digestion, preserve nutrients, reduce odor, minimize foaming, and decrease crusting. Disinfectants are used in swine production facilities to reduce disease transmission, improve animal health and welfare, and increase growth efficiency. Research on manure additives has focused mainly on odor control and greenhouse gas emission reduction from stored animal manures. There is concern about the occurrence of animal pharmaceuticals in manure and their potential environmental impacts. There is currently little information available on the effects on additives and disinfectants on the physical properties, chemical characteristics, and antibiotic and antibiotic resistance gene concentrations of swine manure slurry. In this study, six manure pit additive products (Coban 90, Manure Magic, MOC-7, More Than Manure, Sludge Away, and Sulfi-Doxx) and four disinfectants (Clorox, Pi-Quat, Tek Trol, and Virkon) were tested. Swine manure was collected from an operating facility in Nebraska and loaded into 57 L reactors, where the manure was dosed with one of the tested additives or disinfectants following the manufacturer’s instructions. Baseline testing was performed to establish the physical and chemical constituents present in the manure prior to dosing, and chlortetracycline, lincomycin and tiamulin were detected in the manure. A control reactor with no additive or disinfectant dosing was also operated. The reactors were maintained for 40 days and samples from the reactors were taken for analysis of physical and chemical manure properties, nutrients, antibiotic levels and abundance of antibiotic resistance genes over time. When compared to the Control treatment, the introduction of additives did not significantly
reduce quantities of the physical properties, chemical characteristics, or antibiotic concentrations of swine slurry. The presence of disinfectants resulted in a significant increase in the observed concentrations of chlortetracycline and tiamulin with time, which we attribute to the breakdown of solids within the slurry. The disinfectants were overall more effective in reducing the absolute abundance of ARGs as compared to the pit additives. Out of the four disinfectants tested, Tek-Trol was the most effective treatment in reducing the absolute abundance of ARGs as compared to the Control. These results indicate that swine pit additives and disinfectants can influence the concentration of constituents in swine manure slurry, including nutrients, antibiotics and ARGs, that may then be land applied. Further testing is recommended at an operating facility to confirm our findings from laboratory scale reactors.