Dry matter intake (DMI) regulation is important in ruminants as DMI is a major determinant of milk and meat production. It is known that the gut peptides glucagon-like peptide-17, 36 amide (GLP-1) and cholecystokinin-8 (CCK) can reduce DMI in nonruminants (Walsh, 1994). In ruminants, there is little information on the function or effects of diet on plasma concentrations of these peptides. Previous studies have shown that supplemental dietary fat (Relling and Reynolds, 2007b) increases plasma concentrations of GLP-1 and CCK and decreases DMI. In contrast, increased metabolizable energy intake (MEI) in early lactation also increases GLP-1 and CCK concentration in dairy cows (Relling and Reynolds, 2007a). Therefore, our objective was to determine if plasma concentrations of GLP-1 and CCK are affected by supplemental fat, and if the response differs for ad libitum versus restricted DMI.