No data are available concerning the ADME of modified celluloses in the target animal species. However, the absence of significant metabolism in the rat and the human indicates that, despite an increase of water solubility, the etherification of cellulose would strongly limit the action of microbial cellulases. Consequently, the FEEDAP Panel considers that the lack of digestibility of these compounds in monogastric mammals, poultry and fish is likely to occur. In ruminants and hindgut animals (rabbit and horse), it cannot be excluded that the rich and complex microbiota would allow a limited enzymatic attack of these structures.