Numerous dietary and cow factors and interactions affect DMI. Conrad et al. (1964)) described the general framework of intake regulation by dairy cows, which is still applicable today. Basically, they described a 2-phase control system in which either gut fill or energy demands regulated intake. Gut fill is a function of size of the cow and size of the rumen and gastrointestinal tract. Energy demand is a function of BW, milk production, and stage of lactation or gestation (i.e., differential partitioning of energy to milk or body reserves). In early lactation, cows are usually in negative energy balance, suggesting that fill, not energy demand, regulates intake. In mid to late lactation, cows usually are in positive energy balance, suggesting that energy demand, not fill, regulates DMI. Supplemental fat can affect DMI differently depending on stage of lactation (Chilliard, 1993; Drackley et al., 1998; Onetti and Grummer, 2004).