Dietary protein is strong appetite inhibitor as it reduces food intake in following meals by signaling directly or indirectly to the brain, modulating eating behavior. However, the type of protein in snacks or pre-loads differently influences food intake, likely due to differences in dietary protein hydrolysis and amino acid bioavailability. We recently observed striking differences in plasma amino acid kinetics as well as intra-gastric behavior between micellar casein (MC) and sodium caseinate (SC). Gastric distension and plasma amino acid levels, in particular that of leucine, both impact food intake. The objective of the present study was therefore to clarify whether the structure of casein impacts its preload effect on subsequent food intake in the pig model. Overnight fasted pigs (21.5 ± 1.5 kg) equipped with jugular catheters were allowed to consume within 5 min casein drinks differing in casein structure (SC vs. MC, 350 kcal, 10% casein, 1.2% glucose in water) in a cross-over study. Ad libitum intake of their regular feed was assessed during 1hr, either 1 or 4hr after casein drink ingestion. Gastric emptying of the casein drinks radiolabeled with 99Tc- colloïd was followed during 2hr using gamma-scintigraphy. Plasma kinetics of hormones related to eating behavior (ghrelin, GLP-1, insulin) and of free amino acids were evaluated for 2hr following casein drink ingestion. The amount of feed consumed 1hr, but not 4hr, after SC ingestion was lower than the amount of feed consumed after MC ingestion (feed consumed at 1h: SC 1306 ± 138 vs. MC 1513 ± 79 g, P=0.03). Gastric emptying parameters after both types of casein ingestion were not significantly different (t1/2: SC 103 ± 12 vs. MC 116 ± 18 min, β: SC 0.67 ± 0.14 vs. MC 0.52 ± 0.04, P>0.05). Plasma ghrelin, GLP-1 and insulin kinetics were similar after casein drink ingestion (SC vs. MC, P>0.05 for all hormones). Free plasma amino acid concentrations, in particular that of leucine, increased after both SC and MC ingestion but was greater after SC than MC ingestion from 60 to 120 min (plasma leucine at 60 min: SC 87.8 ± 4.8 vs. MC 66.0 ± 3.5 mg/L, P=0.009). In conclusion, ingestion of casein differing in their structure impacts subsequent food intake likely due to difference in amino acid bioavailability. Casein exhibits less anorectic effect when consumed as micellar casein than as sodium caseinate. Such differences might be of importance when designing food dedicated to people with low appetite.