The Problem: The current need to find alternatives to the use of antibiotics utilization in animal feeds is opening opportunities for feed additives such as phytochemicals in poultry. The present study aims to investigate the effects of supplementing broiler diets with a bioactive pomace-oil extract from Olea europaea (OE) on gut integrity after a challenge of intestinal permeability loss induced by a short-term fasting period. How we investigated or researched the problem: 660 one day old male broiler chicken (Cobb 500) housed in floor pens were randomly assigned to 5 experimental groups (6 pen/treatment, with 22 birds/pen). From a basal diet, four experimental diets were designed, namely a control diet with no additives (CF), supplemented with 100 ppm of monensin (MF) or with 500 (OE500F) and 1500 ppm (OE1500F) of an OE provided by Lucta S. A. (Madrid, Spain). Birds were fed their respective diets ad libitum from 1 to 14 d of age and then were submitted to a 15.5 h short-term fasting period. In addition, a control group was included and fed the control diet without undergo the fasting period (CNF). One hour and half before finishing the fasting period, an oral gavage of lactulose and mannitol sugars was given to two random birds per pen. After the fasting period, selected chickens (n = 12) were slaughtered to collect duodenum to analyze intestinal morphology, ileal mucosa scrapings to analyze the expression of genes involved in gut integrity and immune response and blood to measure sugar permeability marker. Results: Intestinal permeability was significantly (P < 0.001) increased by 15.5 h fasting period as measured by lactulose and mannitol ratio marker. Moreover, duodenal crypt depth significantly (P < 0.001) increased in CF birds compared to CNF. In addition, the expression of Claudin1 was significantly lower (P < 0.05) and inflammatory markers TLR4 and IL-8 were significantly increased (P < 0.05) in CF chickens compared to CNF. Duodenal crypt depth was lower in animals fed the OE500F compared to CF birds (P < 0.05). Furthermore, birds fed the OE500F showed higher serum mannitol and reduced IL-8 expression compared to the CF and OE1500F groups (P = 0.05). In addition, the expression of the B-cell marker (Bu-1) increased linearly with the inclusion of OE in diets.Implications / Conclusions: The 15.5 h fasting period increased intestinal permeability triggering an inflammatory response mediated by TLR4. The supplementation with 500 ppm of OE ameliorated some of the negative effects of increased intestinal permeability after a short-term fasting period.