Inputs of polychlorinated biphenyl residues in animal feeds

Animal nutrition constitutes an important issue for the animal production industry. Products intended for animal feed may contain undesirable substances which could endanger animal health or, because of their presence in livestock products, human health or the environment. In this sense, several incidents related with the presence of persistent organic pollutants, particularly with polychlorinated biphenyls (PCBs), have happen in food and feed additives. Animal feed and feed components are challenging matrices for the determination of residues and contaminants. The variability of these matrices is enormous. It ranges from relatively simple ones like those based on wheat to all kinds of by-products from agro and food industry, such as cereal oils. Firstly, this article reviews and addresses the extraction efficiency of ultrasonic assisted solvent extraction (UASE) and focused ultrasonic solvent extraction (FUSE) for determining selected PCBs in animal feed and ingredients. Detection of these pollutants was carried out by gas chromatography (GC) coupled to electron capture detection (ECD); tandem mass spectrometry (MS/MS) was used as confirmatory technique. Recoveries ranged from 70% to 98% by UASE and from 75% to 106% by FUSE with estimated quantification limits between 0.11 and 0.3 μg/kg in feeds and ingredients and between 0.2 and 0.75 μg/kg in fats. Once the method was optimised, it was applied to 18 feed samples as well as 16 ingredients. PCBs were detected in almost all the selected samples. As expected, the samples of animal origin as shell powder and fish oil showed the highest concentrations of 56 and 29 ng/g, which are equivalent to toxicological concentrations of 123 and 18 ng WHO-TEQDL-PCBs/kg, respectively. Feeds and ingredients from vegetable origin ranged from non-detected to 7.1 μg/kg. PCB 77 and 169 were the discriminant congeners in the selected samples of feed and ingredients. Samples showed that the pattern of PCBs depends on the sources of contamination.