1a. Objectives (from AD-416):
Objective 1. Investigate the kinetics of uptake, metabolism, distribution, and excretion of chemicals in food animals with the goal of reducing public exposure to chemical residues in food animal products (milk, meat, eggs). Objective 2. Determine the fate of endogenous reproductive hormones, pharmaceuticals, and other chemicals in wastes of food animals, including transport through soil and water. Objective 3. Develop sensitive and accurate analytical tools to rapidly detect and quantify chemicals identified in objectives 1 and 2.
1b. Approach (from AD-416):
The broad objective of this project is to determine the fate of natural and man-made chemicals in food animals and in food animal systems (wastes, soil, water). Three broad classes of chemicals will be targeted for study: (1) veterinary drugs or feed additives administered to food animals under extra-label use conditions, (2) endogenous steroid hormones, and (3) novel developmental chemicals of potential utility to the livestock industry. Use of veterinary chemicals in an extra-label manner without knowledge of residue depletion kinetics has led to unsafe residues in meat products. Endogenous steroid hormones excreted by livestock are highly potent endocrine-disrupting compounds that are thought to disrupt the development of aquatic species after their entry into surface waters. Finally, chemical technologies developed by the ARS, e.g., chloroxyanions and nitro compounds, are active against Salmonella and E. coli pathogens in livestock immediately prior to slaughter, but the impacts of chemical residues in meat products have not been fully investigated for these compounds. Regardless of the chemical class being investigated, the development of sensitive and accurate analytical tools is critical completion of the objectives. Therefore, a significant portion of the project is devoted to developing the analytical tools required to ensure success of the project. The overall project goal is to understand the broad impact that chemical residues play in influencing food and environmental safety.
3. Progress Report:
Fecal levels of generic E. coli were enumerated after oral or intravenous dosing of equivalent amounts of sodium chlorate. Blood levels of chlorate increased rapidly after oral or intravenous dosing and fecal sodium chlorate levels were low. Fecal E. coli levels were decreased by oral or intravenous chlorate administration. Such results strongly suggest that sodium chlorate salts act at a systemic level to reduce fecal E. coli excretion. Fate and disposition studies were conducted with labeled chlorine dioxide gas on edible fruits, vegetables, and/or melons. Regardless of the crop group tested, the most prevalent chlorine dioxide metabolite was chloride ion (a natural product). In some cases, residues related to chlorine dioxide treatment were completely absent from edible tissues. Such results suggest that chlorine dioxide gas could be a viable method for removing pathogens from produce intended for human consumption. A penicillin G procaine residue depletion study was initiated in heavy sows. Heavy sows were treated in an off-label manner to replicate industry practices and sows were killed with withdrawal periods ranging from 5 to 39 days. Tissues were collected from each animal for qualitative and quantitative analyses. The live phase of the study has been completed and analysis of tissues is underway. The fate of estradiol was monitored for 42 d in laboratory-scale anaerobic digesters. Estradiol decreased rapidly in the liquid layer of the digester and reached steady state concentrations by 4 days at about 20% of the initial dose. Estrogen was rapidly transformed to estrone, which adsorbed quickly to sludge; about 25% of the estradiol was metabolized to methane. A large decline in estrogen will occur during anaerobic digestion and coupling the anaerobic process to aerobic treatment may serve to completely destroy all estrogen. Chlortetracycline is an antibiotic frequently utilized in swine production. Because chlortetracycline is excreted unchanged in the feces, relatively high amounts are found in hog wastes. A sensitive and specific analytical method was developed to measure chlortetracycline and its degradation products in hog wastes. The method was used to determine chlortetracycline and its degradation products as a function of time in swine manure incubated at three different temperatures. Higher temperatures accelerated the decomposition of chlortetracycline and the formation of isochlortetracycline, a product with little or no antibiotic activity. Environmental loads of chlortetracycline may be overestimated if the method of analysis does not distinguish between chlortetracycline and isochlortetracycline.
1. Development of a rapid screening assay for the antibiotic roxarsone. Roxarsone is used in the poultry and swine industries as a feed additive to treat coccidiosis and other intestinal disorders as well as to improve feed efficiencies and weight gain. A rapid screening method was developed by ARS scientists at Fargo, ND, using antibodies against roxarsone in an immunoassay format. The immunoassay was suitable for the determination of roxarsone in chicken meat, having good sensitivity and specificity. The assay was able to detect roxarsone well below the maximum allowed food residue level. Because of its sensitivity and specificity the assay could be adapted to high throughput or on-site residue screening programs.
Shappell, N.W., Mostrom, M.S., Lenneman, E.M. 2012. E-Screen evaluation of sugar beet feedstuffs in a case of reduced embryo transfer efficiencies in cattle: the role of phytoestrogens and zearalenone. In Vitro Cellular and Developmental Biology - Animals. 48:216-228.