Bypass fats (BF) are usually referred to as escape fat, ruminal inert fat or protected fat and are more costly per unit of energy provided compared to commodity fats. BF and prilled fat (PF) supplementation are a viable option to mitigate negative energy balance (NEB) and also to improve high yielding lactating animal performance. Supplementation of fat with calcium salts of long chain fatty acids approach is a good method for increasing energy density of the diet and to improve milk yield, fat content and reproductive performance but it partially degrades in the abomasum and on the other hand prill fat (PF), a bypass fat available in different forms augments productive performance of lactating animals by getting digested only in the small intestine. It is a well-established fact that inclusion of energy as unprotected fat higher than 3-4% cause physical and chemical changes in the microbial fermentation in rumen resulting in decrease in microbial activity and depression in cellulose digestibility. Hence, inclusion of the fat in ration of lactating animals which is resistant to bio-hydrogenation by rumen microbes reduces the risk of metabolic acidosis and later on gets digested in lower digestive tract. Adding protected fat to dairy rations positively affect the efficiency through a combination of calorific and non-calorific effects.