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Antibiotics in Animal Waste Lagoons Antibiotic levels in manure and logoons vary widely. Raising livestock for meat, milk and eggs has been an integral part of food production in the United States for centuries. The efficiency of the U.S. food production system is unsurpassed, and currently less than 2 percent of the population is involved with the production of food for the rest of the country. The high level of production efficiency can be attributed to scientific advances in breeding, genetics, nutrition, and animal health on the farm. Veterinary medicines or drugs have become a critical component of the food-animal production system providing benefits related to animal health and growth efficiency. Since the benefits of sub-therapeutic use of antibiotics were discovered over 40 years ago, more and more animal feeding operations have begun using feedstocks fortified with these compounds for enhancing growth and feed efficiency. Additionally, the sub-therapeutic use of antibiotics in livestock has been credited with allowing concentrated animal feeding operations to exist, a key reason that the U.S. animal production system has become so efficient. The advances that have been made in food production efficiency would not have been possible without gains in controlling disease in crops and animals. To a large degree, these gains are due to pesticides for crops and veterinary drugs for animals. The success of these chemicals in controlling disease has not come without negative side-effects. For example, the impact of pesticides on the environment has been well documented, and research has led to compounds that are less persistent and less mobile. We also have developed best management practices (BMPs) for accomplishing agricultural objectives with minimal impact on the environment. We are not nearly as far along with the process of understanding the impact of veterinary medicines on the environment or developing BMPs to minimize those impacts. A critical question surrounding the recent discovery of antibiotics in the environment is the ultimate source: domestic wastewater, animal agriculture, or other sources. The objective of this study was to begin measuring the occurrence of a range of antibiotics in suspected sources. This document will describe the results of an occurrence survey of these compounds in liquid and solid residues associated with animal feeding operations, manure and lagoon water. Measurement of relatively low concentrations of complex organic compounds in manure and lagoon water matrices is challenging. Methods that combined liquid-liquid extraction, solid-phase extraction, liquid chromatography and mass spectrometry were developed for quantifying three classes of antibiotics in manure and lagoon water matrices. The antibiotics that were measured included five tetracyclines (TCs) (tetracycline (TC), oxytetracycline (OTC), chlortetracycline (CTC), doxycycline (DXC), and democlocycline (DMC)), six sulfonamides (sulfathiazole (STZ), sulfamerazine (SMR), sulfamethazine (SMT), sulfachloropyridazine (SCP), sulfamethoxazole (SMX), and sulfadimethoxane (SDM)) and three macrolides (tylosin (TLS), erythromycin (ETM) and roxythromycin (RTM)). The waste streams from 25 animal feeding operations in Colorado were sampled for either manure, lagoon water or both. The number of operations that were sampled for each waste stream is shown by livestock type in Table 1.
The range of results for each class of animal antibiotic is shown in Table 2 for the lagoon water and Table 3 for manure samples.
The results of this occurrence survey indicate that a wide range of antibiotics is present in most animal waste streams, either runoff ponds, waste lagoons or manure stockpiles. The individual antibiotic results varied widely. For example, tylosin (a macrolide) was found in all but four waste lagoons sampled (an occurrence rate of 84%) but erythromycin and roxythromycin were found in only 36% and 10% of the lagoons sampled, respectively. Tetracycline (occurrence rate of 96%) and sulfadimethoxane (occurrence rate of 44%) were the most common compounds in their classes. The concentrations of the antibiotic compounds also varied significantly as shown in Tables 2 and 3. The wide range of concentrations seems to indicate that feeding practices along with waste management procedures can significantly impact the fate of antibiotics in waste streams. The next phase of the project will attempt to relate these practices with antibiotic concentration in lagoons and manure stockpiles. We hope to be able to provide guidance and BMPs to the animal agriculture industry on how to minimize the release of antibiotics to the environment. Since the data indicates that a significant amount of antibiotic compounds can concentrate in the manure, we will also study how manure management techniques influence the transport of antibiotics to the environment. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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