Degradation of Abamectin and Doramectin on Sheep Grazed Pasture

Abstract

Avermectins are widely used veterinary medicines. They bind strongly to faeces in their non-metabolized form and their half-life in faeces depends on field conditions. There are conflicting data regarding the behaviour of avermectins in the environment. Therefore, we investigated the degradation of abamectin and doramectin on sheep grazed pasture under field conditions in soil, soil-faeces and faeces samples from day 6 to day 70 (abamectin) or to day 50 (doramectin) after sheep treatment. Field conditions were recorded periodically during the experiment. Degradation of abamectin in sheep faeces and in soil-faeces was observed until day 60, with small amounts present in faeces until 70 days post treatment. Because the concentration of abamectin residues in soil was very low on day 6 after treatment, further significant degradation could not be measured. The concentration of doramectin in all analysed matrices decreased rapidly until day 50. It can be concluded that high concentrations of both avermectins were present during the first 20 days after treatment and that field conditions have an important role in degradation of avermectins on grazed pasture of treated animals. Clear identification of the consequences of avermectin exposure and the period of the greatest environmental risk will require further investigations.

Soil Nutrients, Bacteria Populations, and Veterinary Pharmaceuticals across a Backgrounding Beef Feedlot

“…The average monensin, lasalocid, and doramectin concentrations in the GR area soils were, respectively, 50, 12, and 6 times lower than the FD area. The GR area soils contained 1.89 ng g −1 monensin, comparable to the values (0.30 —1.0 ng g −1 ) reported by Kolar et al (2006) and Erzen et al (2005) for soils and dry sheep feces mixture in sheep‐grazed pasture. However, the GR area contained a 5 times lower doramectin concentration than the 10.1 ng g −1 (50 d after) reported by Erzen et al (2005) for the same type of soil material.…”

“…The GR area soils contained 1.89 ng g −1 monensin, comparable to the values (0.30 —1.0 ng g −1 ) reported by Kolar et al (2006) and Erzen et al (2005) for soils and dry sheep feces mixture in sheep‐grazed pasture. However, the GR area contained a 5 times lower doramectin concentration than the 10.1 ng g −1 (50 d after) reported by Erzen et al (2005) for the same type of soil material. Differences in animal groups (beef cattle vs. sheep) and management practices adopted in the two experiments may explain the above different results.…”

Laboratory Testing of Sulfamethoxazole and its Metabolite Acetyl‐Sulfamethoxazole in Soil

“…Due to the relevance of biologically active substances in soil environments [11,12], numerous fate monitoring studies were focused on pharmaceuticals in soils. Processes under study were sorption and transport in soils [13][14][15][16][17][18], surface runoff [19][20][21] and degradation [22,23]. In order to understand these processes and their depen-dencies on the entry routes of pharmaceuticals in soils in more detail, a research concept based on a sequence of sophisticated laboratory tests was designed by Kreuzig et al [24] and Kreuzig and Höltge [25].…”

Fate of the Benzimidazole Antiparasitics Flubendazole and Fenbendazole in Manure and Manured Soils

“…Processes under study in laboratory or field scale focused on degradation in manure [1 -3], sorption and transport in soils [4 -9], surface runoff [10 -12], degradation [13,14] and ecotoxicological effects [15,16]. Test substances under study predominantly belonged to the therapeutical groups of antibiotics, e. g., sulfonamides, tetracyclines, or to macrolide endectocides, e. g., ivermectin.…”