Laboratory Experience with the Microscopic Method for the Detection of Insects in Poultry Feeds.

Introduction: The use of insects and their processed animal proteins (PAPs) for animal nutrition creates the need for research into methods useful for routine surveillance for their presence. The aim of this study was to evaluate a modified microscopic method for the detection of particles of insects in poultry feed. Material and Methods: A total of 90 samples including PAP of insects (Hermetia illucens and Tenebrio molitor), poultry feeds produced with different levels (0-27%) of insect PAP content, and other poultry feeds spiked with insect PAP at 1% were investigated using a modified microscopic method with a double sedimentation protocol. Results: Characteristic features of insects including cuticulae, muscles, bristles and tracheoles were determined in the microscopic images obtained. In all spiked samples, characteristic fragments of insects were detected. The fragments of muscle and tracheoles only indicated the presence of material from members of the insect class but could not facilitate identification of organisms to species level. Conclusion: The results obtained with this double sedimentation protocol for the isolation of insect PAP from feed for poultry have shown that the method can be used in routine analysis.

Development and application of criteria for classification of hydrolysed proteins in the framework of feed safety.

In the view of a circular economy, there is an increasing need for (re-)using animal by-products that have a wide range of applications and sufficient safety. Hydrolysates of animal proteins (HPs) are frequently used as feed ingredients. Nevertheless, clear criteria for legal use and methods for monitoring feed applications are not available. Here, a range of methods have been used and evaluated for characterizing a set of 26 samples of hydrolysed proteins, 'hydrolysed' feather meals and processed animal proteins (PAPs), with verification based on an additional set of eight samples. Methods included determination of ash content, sediment (mineral fraction) content, protein content, species identity, solubility, protein solubility, size exclusion chromatography and polyacrylamide gel electrophoresis (SDS-PAGE). After a comparison of results obtained with water and SDS, water was chosen as the solvent for environmental and occupational reasons. Typical HP samples have a protein content higher than 60%, a solubility exceeding 50% and a virtual absence of a mineral fraction. The first discrimination between HPs and PAPs could be based on the absence or presence, respectively, of a mineral fraction. An approach for HP characterization is designed using a Hydrolysation Index (HI) based on the fraction of peptides smaller than 10 kDa, the solubility of the sample and the fraction of soluble proteins. A simplified version (HIs), exclusively based on the fraction of peptides smaller than 10 kDa and the solubility of the sample, shows a trend among the samples highly comparable to HI. Values for HI and HIs exceeding 60% would characterise HPs. Feather meals, which are heat treated instead of treatment by a chemical process of hydrolysation, range among the PAPs and should not be indicated as "hydrolysed." The HIs can be used as an easy parameter for classifying HPs and for legal enforcement.