Abstract
The insecticidal activity of parasiticide residues in dung of cattle treated with a sustained release eprinomectin formulation was examined, and an improved eprinomectin dung residue extraction method is presented. Emergent insect abundance and richness were significantly reduced in all post-treatment intervals (7, 14, 28, 56, 84, 112, and 140 d), relative to pre-treatment. Emergent insect diversity was reduced for between 84 and 112 d post-treatment. Collembola were not affected by residues. Chemical analyses subsequently documented residues of eprinomectin in dung of each collection period post-treatment at levels expected based on previously reported excretion profiles for this product. Cattle subcutaneously injected with this product excreted residues that reduced dung-breeding insect emergence for 5 mo post-treatment. The consequences of these long-term non-target effects to pasture ecosystems are not known.
Highlights
Avermectins are veterinary parasiticides used on livestock
Eprinomectin from topical application had lower maximum plasma and dung concentrations and longer mean retention times in plasma and dung compared to eprinomectin administered by subcutaneous injection [2]
Cattle treated with eprinomectin in the LongRange formulation excreted eprinomectin in a bimodal manner with dung concentration maxima near day 14 and 84
Summary
Avermectins (e.g., doramectin, ivermectin, eprinomectin) are veterinary parasiticides used on livestock. Avermectins are minimally metabolized in livestock, are fecally-excreted and have insecticidal activity [1]. Application methods include use of an oral paste, subcutaneous injection, topical application, and sustained release boluses administered orally to the rumen. Eprinomectin from topical application had lower maximum plasma and dung concentrations and longer mean retention times in plasma and dung compared to eprinomectin administered by subcutaneous injection [2]. The prolonged dung excretion of topical avermectin formulations reduced adult insect emergence in dung of treated cattle for up to 84 d [3] and 112 d [4] postapplication. Residues in dung of cattle treated with ivermectin applied in a sustained release bolus killed dung beetle larvae for up to 143 d [5]
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