author(s)
Alok Mishra, Ganesh N Aderao, Sandeep Kumar Chaudhary, Kanti Raje, Akansha Singh and Preeti Bisht

abstract
Niacin has an affirmative role on curtailing heat, nutritional stress in lactating animals due to its role in the physical regulation of body temperature by vasodilatation besides its potent role in counteracting ketosis. As the component of coenzymes NAD and NADP, it is crucial in energy metabolism. Moreover, there is the synthesis of niacin by rumen microbes in ruminants, therefore, niacin reaching duodenum is higher than niacin fed. The niacin so formed will help in the growth of rumen microbes and will aid in fiber degradation favoring acetate production which may appear in milk as milk protein and milk fat, respectively. Also, it has a role in DNA repair and cell signaling. It has been indicated to have a role in the increased synthesis of heat shock protein (HSP) that are crucial in ameliorating heat stress. Niacin However, there are different opinions among researchers regarding the effect of niacin on the milk yield, composition and physiology of lactating dairy cows during hot weather. Therefore present review discusses the effect of niacin supplementation on milk yield, milk composition and physiological responses of lactating cows during heat stress.