This article (open access) discusses some of the current challenges in testing animal feed for compliance with European legislation using microscopy (one of the official methods mandated by the legislation).
Although the article is pre-publication and not peer-reviewed, it is generously illustrated with colour photographs of microscope slides - such as that shown here - which could be a valuable training aide to Official Control analysts who are relatively new to microscopy. The author discusses key areas where expert interpretation is needed, describing the examples of bovine spray-dried plasma protein (legal, within restrictions, in the US but banned in the EU in ruminant feed), differentiating milk powder from blood powder, and differentiating hydrolysed proteins from vegetable vs animal sources.
