Using animal manure as organic fertilizer to grow fodder crops is causing public health concerns because animal manure is the major reservoir of veterinary antibiotics. In this study, we used a mathematical model to estimate the risk of human exposure to veterinary antibiotics when using swine manure as organic fertilizer to grow alfalfa (Medicago sativa L.). Alfalfa was planted in a greenhouse and fertilized with swine manure spiked with oxytetracycline (OTC, at 0, 150, and 1500 mg/kg of manure), ofloxacin (OFL, at 0, 15, and 150 mg/kg), or sulfamonomethoxine (SMM, at 0, 5, 15 and 150 mg/kg). Alfalfa was harvested at the budding stage and ensiled for 60 days. Results showed that OTC and OFL could be detected in the alfalfa root, stem, and leaf with a concentration ranging from 8.85 to 59.17 μg OTC /kg and from 1.50 to 4.10 μg OFL/kg dry matter, but SMM could only be detected in the root ranging from 29.10 to 63.75 μg/kg dry matter. The ensiling for 60 days decreased the OFL concentration by 68.7% but only slightly decreased the OTC concentration. The maximum daily exposures of humans to OTC and OFL through liquid milk consumption were estimated to be 5.84E-8 and 1.63E-8 μg, respectively, both of which are well below the intake levels of OTC (72 μg) and OFL (54 μg) mandated by the European Union. The results of the present study indicate that using swine manure as organic fertilizer to grow alfalfa poses a limited risk for human exposure to veterinary antibiotics through the consumption of liquid milk. © 2021
Tag: manure
Effect of fertilizer inputs on productivity and herbage quality of native pasture in degraded tropical grasslands
The practice of applying fertilizer inputs on an unimproved natural pasture is limited in tropical grasslands. A study was conducted to evaluate the response of degraded natural pasturelands in terms of species composition, forage yield, and quality to the application of different types of fertilizer. The study was conducted in two districts in the central Rift Valley of Ethiopia with contrasting agroecologies. The treatments were control (no application of fertilizer), commercial fertilizer (50 kg urea ha–1 and 100 kg diammonium phosphate [DAP] ha–1), cattle manure (7.5 t ha–1), wood ash (3 t ha–1), and lime (7.5 t ha–1). Soil physical properties were not altered following application of the treatments, but chemical properties, including soil pH (P < .01), electroconductivity (EC) (P < .001), total nitrogen (TN), and P (P < .001) were affected. Soil TN increased from 0.11 to 0.32% following the application of cattle manure. The pH increased from 5.9 to 7.3 with wood ash application. Herbage dry matter (DM) yield increased (P < .001) from 1.88 to 6.65 t ha–1 with chemical fertilizer. The herbage crude protein content increased (P < .01) from 96 to 157 g kg–1 with manure application. On the other hand, the neutral detergent fiber tended to decrease (P < .05) following manure application. Partial cost-benefit analysis indicated a positive economic gain from the direct sale of pasture hay for all treatments except for lime. The results indicated that fertilizer inputs offer feasible options to improve pasture productivity and enable rural farmers to benefit from their land resources.