Effect of Antibiotics in Beef Cattle Feces on Nitrogen and Carbon Mineralization in Soil and on Plant Growth and Composition

Abstract

The potential human health hazard associated with the use of antibiotics in animal feeds is currently being reevaluated by the Food and Drug Administration. This study was conducted to investigate the impact of the addition of antibiotic‐containing feces on soil biological activity. A total of nine beef cattle were placed on either a control feed, or a feed supplemented with chlortetracycline (CTC) or oxytetracycline (OTC) for a period of 10 days. Feces from these cattle were collected and analyzed for chemical, physical, and microbiological properties. Samples of the feces were added to an Evesboro sandy loam at rates equivalent to 0, 9.4, and 18.8 dry metric tons/ha (0, 20, and 40 wet tons [U.S.]/acre). Carbon and nitrogen mineralization were studied in the soil‐feces system. Analyses of the feces indicated antibiotic‐related changes in several properties. Total nitrogen in the feces of cattle receiving OTC was, at 1.50%, significantly lower than the 1.74% level found in the feces of CTC fed cattle. Feces from cattle receiving OTC contained a higher concentration of potassium, more fungi, and fewer volatile solids than did wastes from control animals. Antibiotics in the feed had no effect on number of total bacteria, total and fecal coliforms, or fecal streptococci; concentration of NH4‐N, NO3‐N, P, Ca, Mg, Na, Zn, Mn, Fe, or Cu; pH; percent moisture; or chemical oxygen demand in the feces. The antibiotics CTC and OTC were found at levels of 5.3 and 11.3 µg/g, respectively, in the feces of cattle receiving the antibiotics. When added to the soil, feces from antibiotic‐fed cattle evolved approximately 20% more carbon than did control feces during a 70‐day period. Nitrogen immobilization occurred for 28 days following feces addition to the soil. No significant differences due to the use of feces from antibiotic‐fed cattle were observed in the rate of nitrogen mineralization in the soil during a 60‐day incubation. Greenhouse experiments using feces from antibiotic‐fed cattle as a soil amendment demonstrated no changes related to the antibiotics in the growth, yield, or elemental composition of 30‐day‐old corn seedlings (Zea mays L.).

Transport of Pharmaceuticals in Columns of a Wastewater‐Irrigated Mexican Clay Soil

“…A back‐on‐the‐envelope calculation showed that the additional amount of CO 2 –C that was released from the columns was almost four orders of magnitude greater than the amount of carbon that was added with 20 μg L −1 of erythromycin. Similar to our findings, Patten et al (1980) and Fründ et al (2000) reported higher CO 2 evasion from soils that were amended with manure which contained tetracyclines than from control soils. In line with these findings, Höper et al (2002) found elevated metabolic quotients for soils treated with tetracyclines compared to untreated soils.…”

“…The small effect of pharmaceuticals on nitrate leaching and N 2 O emission is probably the result of limited aeration of the clayey soils, which impeded nitrification of the added ammonium, as reflected in small nitrate concentrations of approximately 8 mg L −1 in the outflow. Similar to the results of this study, Patten et al (1980) did not observe an effect of tetracyclines on N mineralization. In addition, we did not observe a significant effect of pharmaceuticals on CH 4 in our experiment.…”

What Do We Know about Antibiotics in the Environment?

“…Influences on the microbial composition in soil were also demonstrated by Hossian and Alexander (1984), in environmentally irrelevant concentrations. Growth of fungi seems to be favoured by the existence of antibiotics in soil as proved by Patten et al (1980).…”

What Do We Know about Antibiotics in the Environment?

“…Strong inhibitory effects on several bacteria and reduction in the length of the hyphe of active moulds in forest soil have been observed when antibiotics are added in concentrations of 10 mg kg-1 soil (Colinas et al1994). Antibiotics in the soil seem to favour fungal growth (Patten et al 1980). Antibiotics in the soil seem to favour fungal growth (Patten et al 1980).…”