Swine farming is one of the major food-animal industries in the nation. In 2003, pig growers in the US had an inventory of 59.6 million pigs and hogs1. On an average, a pig produces about 3.9 kg of manure (a slurry of urine and feces)/day2. Thus, about 2.3 x 108 kg of manure is generated each day in the US by the pig industry. Manure is land applied because its value in supplying nutrients to crops as well as of disposing unwanted waste. Since potent estrogens such as estrone (E1), 17?-estradiol (E2), and estriol (E3) are excreted through the animals’ urine and feces into the environment, storage of large quantities of manure on site may present a serious environmental problem. When pig manure is stored in pits or lagoons, these estrogens may undergo extensive biological (due to microbial enzymes) and chemical transformations3,5. At present, information regarding the fate of estrogens in pig manure is lacking due to the lack of standardized analytical methods to quantitatively measure different estrogens and their metabolites in manure and environmental waste. Therefore, the aims of this study are to (1) develop methods for determination of estrogenic capacity, and estrogen screening and conformation in liquid and solid pig waste; and (2) study the fate and transport of estrogens from land application of pig waste containing estrogens from pig excreta.
In this project, ELISA methods were developed for rapid screening of different estrogens, a VIT- based method was validated for screening of estrogen activity, and mass spectrometry methods were developed for confirmation of estrogens in urine, feces, and stored manure samples collected from about different farms. These methods were used to study the fate of estrogens in manure samples. This study showed that pig urine contained conjugated (inactive) estrogens, while pig feces to contain ‘free’ (active) estrogens. Conjugated estrogens will not bind, but ‘free’ estrogens will strongly bind the solid part of manure and soil particles. Since conjugated estrogens are biologically inactive, these estrogens may not have much environmental impact. However, possibility exists that the conjugated estrogens may get hydrolyzed resulting in an increase in its estrogenic activity.
We also observed that both conjugated and free estrogens bound to the solid particle of manure and were not available for leeching. This indicated possibility that, although the estrogenic activity of manure may increase due to the hydrolysis of conjugated estrogens, the active estrogens may not migrate to distant sites. Estrogens will mostly remain at the site of production.