Niacin (Vitamin B3) is significantly important for the metabolism of animals and human beings due to its incorporation into the coenzymes NAD and NADP. For dairy cows, the microbial synthesis of niacin in the rumen is an important source besides its availability from feed and endogenous formation. This vitamin is involved in various energy-yielding pathways and for synthesis of amino acid and fatty acid; for which it is important for milk production. Supplementation of niacin has beneficial effects on growth of cattle. The production performance of dairy cows fed with niacin at 6g/day may not be satisfactory, but supplementation of 12g of niacin per head per day can increase milk production by about 1lb. An optimistic return on asset is possible if the supplementation is limited to high producing early lactation cows. Supplementing the dairy animals with a dose of 6-12g of niacin will not only protect them from various metabolic diseases but will also help them defend from severe heat stress; ultimately leading to augmentation of their health, production potential and economy.