Proper protein and energy nutrition is very important for optimizing the productivity of milch animals. Milk urea nitrogen (MUN) is a simple and non invasive tool that can be easily employed to assess the protein and energy nutrition of dairy cattle in a given sitution. In the present study, the base line MUN in crossbred cows and graded Murrah buffaloes maintained under village conditions under semi-intensive system or in an organized farm under intensive systme of management was studied and the effect of factors such as production, nutrition and managemental variables on MUN was recorded. Further, the MUN in animals with history of repeat breeding was also studied. The diets of animals in the given situations were evaluated using CNCPS verison 5.0 and optimized diets were formulated to see the effect of such diets on MUN of repeat breeding animals. The study was useful in manywasy such as gaining knowledge on the base line MUN levels, MUN in repeat breeding animals, evaluation of the current feeding practices and how optimized diets can be formulated to reduce feed wastage.