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We studied the influence of pre-hatch egg weight (EW) and the inclusion of oat hulls (OH) in the diet on gastrointestinal tract (GIT) traits and growth performance of pullets reared under stress conditions early in life. There were 14 treatments organized as a 7 × 2 factorial with 7 EW groups (47.0 to 54.0 g differing in 1 g between groups) and 2 inclusion levels of OH in the diet (0 vs. 3%). The pullets were reared under a series of stresses early in life (no access to feed for extended time post-hatching, reduced accessibility to feed and water at arrival to the farm, reduced ambient temperature at night, low light intensity, and hot-blade beak trimming at 18 D of age). Feed intake, BW gain, and FCR were measured by period (0 to 5, 5 to 10, and 10 to 16 wk of age) and cumulatively. Data were analyzed as a completely randomized design with EW and OH inclusion as main effects. In addition, EW effect was partitioned into linear and quadratic components. The stress conditions applied affected similarly the growth and GIT development of the pullets, independent of EW. An increase in EW increased BW at hatch and at 5 wk of age linearly (P < 0.05), but no effects were detected thereafter. Oat hulls inclusion increased ADFI and impaired FCR (P < 0.05) from 0 to 5 wk of age but did not affect energy efficiency at any age. At 5 wk of age, the relative weight (% BW) of the GIT decreased linearly (P < 0.05) with increases in EW and increased with OH inclusion (P < 0.05). Oat hulls inclusion increased the relative weight of the gizzard at all ages (P < 0.01). In conclusion, egg weight did not affect pullet growth from hatch to 16 wk of age. Independent of the initial BW of the pullets, OH inclusion improved gizzard development at all ages without affecting growth performance., (© 2019 Poultry Science Association Inc.)