The effects of inclusion of pea hulls (PH) in the diet on growth performance, developmen of the gastrointestinal tract and nutrient retention were studied in broilers from 1 to 18 do age. There were a control diet based on low fibre ingredients (69.3 total dietary fibre (16.1 crude fibre/kg)) and three additional diets that resulted from the dilution of the basal die with 25,50 and 75 g PH/kg (81.2, 93.2, and 105.1 g total dietary fibre/kg diet, respectively: Each treatment was replicated six times and the experimental unit was a cage with 1; chicks. Growth performance, development of the gastrointestinal tract and the coefficient. of total tract apparent retention (MAR) of nutrients were recorded at 6, 12 and 18 d of age In addition, jejunal morphology was measured at 12 and 18 d and the coefficients of appar ent ileal digestibility (CAID) of nutrients at 18 d of age. Pea hulls inclusion affected all thi parameters studied. The inclusion of 25 and 50g PH/kg diet improved growth performano as compared to the control diet. The relative weight (g/kg body weight) of proventriculu: (P<0.01), gizzard (P<0.001) and ceca (P<0.05) increased linearly as the level of PH in th; diet increased. The inclusion of PH affected quadratically (P<0.01)villus height:crypt dept1 ratio with the highest value shown at 25 g PH/kg. In general, the MAR and CAID of nutri ents increased linearly and quadratically (P50.05) with increasing levels of PH, showin; maximum values with PH level between 25 and 50 g/kg diet. We conclude that the of the digestive organs increases with increasing levels of PH in the diet. In general, thc best performance and nutrient digestibility values were observed with levels of PH withir the range of 25 and 50 g/kg. Therefore, young broilers have a requirement for a minimurr amount of dietary fibre. When pea hulls are used as a source of fibre, the level of tota dietary fibre required for optimal performance is within the range of 81.2-93.2 g/kg die (25.6-35.0 g crude fibre/kg diet). An excess of total dietary fibre (above 93.2 g/kg diet) migh reduce nutrient digestibility and growth performance to values similar to those observe( with the control diet. (C) 2011 Elsevier B.V. All rights reserved