Animals under desert conditions are suffering from feed shortage and low nutritive value of available feedstuffs. Many desert fodder plants are characterized by its high content of anti-nutritional factors like Tannins which can be detrimental to animals, so using several deactivating materials might be favorable in animal feeding under desert conditions.comparison between Polyethylene glycol (PEG) and Bentonite (as tannins deactivating materials) were discussed and their effects on rumen gas production,feed intake,digestibility,carcass quality and histological changes in animals (sheep) were also discussed.