Plants produce secondary compounds (include tannins, saponins, flavoids, glucosinolates, mimosine and essential oils) which are not used for their growth, development and reproduction of the plant. The review found out the nutrient utilization and productivity performance of ruminant animals supplementing with secondary compounds containing forages, browse species, shrubs, grains, legumes and others. Secondary compounds influence the digestibility, dry matter intake and absorption of nutrients in ruminant’s nutrition. Their dose determines whether they are enhancers or detrimental. Tannins, saponins and essential oils are the major secondary compounds which may improve the health, average live weight gain and milk and wool production. Moreover, ruminant animals consuming secondary compound containing forages support the efficient utilization of energy while reducing the rumen gas production which results in low methane. The main problem of supplementing such kind of forages is the absence of consistent recommended dose. Therefore, this area needs to get more attention and further research should be done to establish much more profitable farm and to boost the economic value of ruminant animals.