In ovo feeding, injecting nutrients into the amnion of the avian embryo, may enhance jejunal nutrient uptake, activity of the intestinal enzymes, and posthatch growth. This hypothesis was tested in the following in ovo feeding (IOF) experiments. In experiment 1, 400 eggs were evenly distributed among 4 nutritional treatments at 23 d of embryonic development (23E) and administered 1 of 4 treatments as a 2 x 2 factorial arrangement of arginine (ARG 0, 0.7%) and beta-hydroxy-beta-methyl-butyrate (HMB 0, 0.1%). Tissues were assayed for maltase, sucrase, and leucine aminopeptidase (LAP) at 25E, hatch, and 3, 7, and 14 d. In experiment 2, all IOF procedures were repeated and treatments were administered at 21E: injected or noninjected control, 21% egg white protein (EWP), 21% EWP + 0.1% HMB. In experiment 3, two hundred eggs were evenly distributed among the following treatments at 23E: noninjected control or 0.7% ARG + 0.1% HMB + 21% EWP. Jejunal samples were assayed for glucose or alanine uptake at 23E, 25E, and hatch (experiment 2), and hatch and 7 d (experiment 3), respectively. All poults were fed a turkey starter diet ad libitum immediately upon hatching. There was a highly significant HMB x ARG interaction on jejunal sucrase, maltase, and LAP activities at 25E and 14 d. Poults in ovo (IO) fed HMB + ARG had approximately a 2- to 3-fold increase in jejunal sucrase, maltase, and LAP activities at 25E, and a 3-fold increase at 14 d, over other treatments. Poults IO fed EWP + HMB (experiment 2) had enhanced glucose uptake at 25E, whereas poults IO fed ARG + HMB + EWP (experiment 3) had enhanced alanine uptake at hatch and 7 d. These studies demonstrate that IOF ARG, HMB, and EWP may enhance jejunal nutrient uptake and digestion in turkeys.