This review was designed to shed light on the applications of rumen-protected amino acids (AA) and choline, undertaken by supplying ruminant's diet with rumen protected bypass products, and their effects on physiological aspects. AA and choline in a hydrogenated palmitic acid matrix, which provides optimum protection, undergo bypass to the rumen compartments, thereby avoiding the physical degradation in this part. Thus, AA and choline involves maximum release, high bioavailability and better absorption rate within alimentary tract. The balancing of ration formula with methionine, lysine, histidine, tryptophan and choline using a rumen protected form, may help to enhance production and permit for better flexibility during diet formulation. Rumen-protected AA and choline result in the most cost-effective solution when formulating dairy diets based balance. Supplementation of rumen protected essential AA and choline is performed to maintain a healthy status, high bioavailable source of these substances, and improve the efficiency of protein metabolism. To sum up, dietary supplementation of rumen protected AA and choline enhances their availability in the gastrointestinal tract and production, with a significant improvement of body conditions, compared to unprotected form. Therefore we recommend using this protected AA and choline continuously in diet formula of ruminants.