Anti-nutrient substances are compounds originating in most animal feed materials that are toxic to animals and limit the accessibility of nutrients to the animal body. But, some Anti-nutrients substances might exercise useful special effects at lower concentrations in feeding material. Main anti-nutritional factors in eatable forage and fodder contain tannins, saponins, phytic acid, gossypol, lectins, amylase inhibitors, goitrogens and protease inhibitors. The balance between anti-nutritional factors' beneficial plus lethal effects depends on their time of exposure, concentration, biochemical structure, and interaction with other dietary constituents. Numerous anti-nutritional factors and noxious elements are present in various foliage utilized as animal feed. Anti-nutrient substances decrease the maximal use of nutrients, particularly minerals, proteins, and vitamins, therefore inhibiting optimum utilization of the nutrients in the feeds and reducing their nutritive quality. High concentrations of tannins (>5.0 g/100 g DM) can be lethal to animals, especially ruminants feeding on tannin-rich forages. Tannins mostly found in legumes binds with proteins, leading to the activation of numerous digestive enzymes and reduction protein digestibility. It is concluded that numerous anti-nutrient substances that affect protein digestibility and the poisonous effects of these substances in plants can be removed or treated to reduce the negative effects using a variety of processing methods such as boiling, fermentation, soaking, germination, and chemical treatment. From the various studies, processing methods can greatly improve the nutritive value of feeding material as feed for ruminants. This review focuses on various categories of anti-nutritional factors, effects of anti-nutritive factors on ruminants, and likely treating methods that could be employed to lessen these factors in animal feeds.