In this research 400 Ross 308 breeder fertile eggs were weighed At day 16 of incubation and evenly distributed into 4 treatments with 4 replicates per treatment and 25 eggs per replicate in a CRD design. On day 18 of incubation, 1 ml of an in ovo feed solution including: I) Carbohydrate (CHO), II) Amino acid (AA), and III) Butyric acid solution in 0.5% saline was injected into amniotic fluid of eggs. The control group remained non-injected. After injection eggs were transferred to hatcher. Upon hatch, chicks were weighed, sexed and transferred to the experimental house and reared to 42 days. At day two the midpoint of the jejunum was sampled for intestinal morphometric examination. The hatchability didn't differ significantly between treatments. Body weight and body weight to egg weight ratio of all in ovo injected hatchlings was greater than in controls (P<0.01). Chicks in ovo fed AA had greatest improvements in body weight gain during 1-21 and 1-42 d period relative to non-injected controls (P<0.05), but without any differences with other injected groups. On day 2 post-hatch villi height in butyric acid injected groups was increased significantly relative to control group (P<0.05). The surface area of an average villus was increased for the CHO, AA and butyric acid in ovo injected groups in comparisson with those of the control group (P<0.05). Effects of in ovo administration of AA, CHO and butyric acid on FCR was not significant. Our results showed that in ovo injection of AA, CHO and butyric acid during last period of incubation can improve post- hatch performance and enteric development.