Supplemental fat may be added to diets to meet the NEL requirement of a cow within fiber and NFC constraints or to increase the NEL intake of cows. In some situations, supplemental fat might be a more economical source of NEL than other ingredients. Replacing digestible carbohydrate with digestible fat increases the NEL concentration in a diet because fat has much higher gross energy and the efficiency of converting digestible energy from fat to NEL is higher. However, at recommended maximum inclusion rates (∼4%), supplemental fat increases dietary NEL concentrations by only about 5%. This means that a very modest 5% decrease in DMI will cancel the increase in NEL concentration, resulting in no increase in NEL intake. Therefore, understanding effects of fat supplementation on DMI under a range of conditions is necessary to develop appropriate supplementation strategies.