The scope for using sunflower cake in ration formulation was tested in 6 horses employed for equine tourism. Three experimental diets providing the same amount of proteins and energy as the control diet were formulated using rising doses of sunflower cake (SD3: 0.3 kg; SD6: 0.6 kg and SD10: 1.0 kg). Digestibility evaluation using internal markers showed that rising sunflower cake doses reduced digestibility of nutrients. Statistical analysis using the diet effect demonstrated a significant reduction in dry matter (DM) (P=0.0006), ether extract (EE) (P=0.0001), crude fibre (CP) (P=0.0279), neutral detergent fiber(NDF) (P=0.0247) and acid detergent fiber(ADF) (P=0.0269) digestibility. Comparison of the two internal markers acid insoluble ash(AIA) and acid detergent lignin (ADL) showed better digestibility values for all measures using ADL. Also glucose and urea showed statistical differences due to diet effect. Manuscript profile