A detailed description of different spiking and coating procedures for the preparation of experimental diets suitable for fish metabolism studies is provided.

Background: Spreading of manure on agricultural soils represents an important pathway by which veterinary medicinal and biocidal products enter the environment. To assess their environmental impact in the context of authorization processes, experimental testing of transformation of these compounds in manure is considered in regulatory guidance documents. However, there is no standardized experimental test method available so far. To fill this gap, an experimental test method was developed to examine transformation in liquid cattle and pig manure. Results: To account for manure specifics and for a possible influence of manure parameters on transformation rates, a comprehensive data acquisition and statistical analysis were performed. To address the variability of liquid manure of different type and origin, 30 manures were sampled and characterized. Thereof, three cattle and three pig manures were selected to perform anaerobic transformation studies with two radiolabeled veterinary medicinal active substances (14 C-salicylic acid and 14 C-paracetamol) and a confidential radiolabeled " 14 C-biocide B" serving as test compounds. Spatial and seasonal variability of manure parameters was quantified, and a sampling technique to obtain homogenous manure samples was developed. Transformation studies with six replicates per sampling point were conducted to examine the influence of test setup, of manure storage conditions, and of parameter variations between manure of the same species and of different species on half-lives, formation of extractable and non-extractable residues and mineralization rates. Finally, a test design was established that yields reproducible results for transformation studies in liquid cattle and pig manure under anaerobic conditions. Conclusions: Results give a reliable basis for an experimental test method to perform anaerobic transformation studies in liquid cattle and pig manure. The developed test method comprises detailed guidance on selection of sampling date and site, collection from manure tank, storage duration and temperature in the laboratory, duration of manure acclimation period, and the incubation system design. It proved to give reproducible results in a validation ring test performed in a follow-up project and is planned to be submitted as draft test guideline for approval by the OECD.

BACKGROUNDDiets used in commercial fish farming use significant proportions of crop‐derived commodities, and it is important to understand the potential for transfer of any pesticide residues on the crop into edible tissues in fish. It is a current requirement in the EU that fish metabolism studies must be performed when a pesticide is used in crops where commodities or processed fractions are fed to farmed fish. Fish metabolism studies in both rainbow trout and common carp have been carried out, following the new working document on the nature of pesticide residues in fish using 14C‐labelled pesticide.RESULTSThe ingestion of experimental diets by rainbow trout and common carp resulted in the uptake and metabolism of the test item, as shown by liquid scintillation counting combined with radio‐thin‐layer chromatography. The metabolite profiles for trout and carp were qualitatively similar regarding the main residue. However, species‐specific differences were found regarding the remaining residue with rainbow trout showing additional metabolites in comparison to carp.CONCLUSIONSMetabolism studies for regulatory purposes can be carried out with both fish species under laboratory conditions. The experimental design reported is suitable for quantifying the transfer of residues to edible tissues and enables characterisation of the chemical nature of residues. © 2015 Fraunhofer Institute for Molecular Biology and Applied Ecology (IME). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.