51. Although it is unlikely that fresh or processed fruit bodies of P. ostreatus will be used as animal feed, fragments of the vegetative mycelium might be consumed. It has been observed that several agroindustrial byproducts locally available in many nations, for example, cocoa pod husks, which when untreated have a limited value as animal feed due to high contents of lignin and non-starch polysaccharides such as cellulose, hemicelluloses and pectin, have improved nutritional utility after they have been chemically modified by being substrates during mushroom cultivation. However, in this case it is recognized that the main proportion of the animal feed ingredient will be the bio-converted agro-industrial byproduct, with mushroom mycelia being only a minor part. When included in this form, oyster mushroom would still be considered a very minor animal feed. No specific studies on the chemical composition of by-products of oyster mushroom cultivation and processing are needed for considering these as animal feeds. Therefore, no specific requirements for constituents to be analysed for animal feed are recommended in this document. Any required compositional information can be obtained from the analysis of proximates performed as part of an assessment for food uses of new varieties of oyster mushroom.