A trial was conducted to evaluate the effect of type of protein and energy sources in pre-starter diet on performance, intestinal microflora and gut morphology in broiler chickens. Pre-starter diets were a 4 × 4 factorial design with 4 levels of isolated soy protein (ISP; 0, 1.5, 3.0, and 4.5%) and 4 levels of broken rice (0, 6, 12, and 18%). All pre-starter diets were formulated to be isocaloric and isonitrogenous. A common commercial grower and finisher diet was fed to all birds from 11 to 24 and 25 to 42 d of age, respectively. Birds fed pre-starter diet contained 4.5% and 18% or 3% and 6% and/or 1.5% and 18% ISP and broken rice, respectively had higher (P < 0.05) body weight gain (BWG) at 42 d of age compared to those fed control or other diets. Chickens fed pre-starter diet contained 4.5% ISP and 18% broken rice had lower (P < 0.05) feed conversion ratio (FCR) as compared to those fed control (1.602 vs. 1.653) or other diets during 1 to 42 d of age. Lactobacillus counts in ileum was reduced (P < 0.05) by 14% when birds fed pre-starter diet contained 4.5% ISP and 18% broken rice compared to control ones at 10 d of age. Bifidobacteria counts in ileum and Escherichia coli counts in ceca were reduced (P < 0.05) when pre-starter diet contained 4.5% ISP compared to control ones at 10 d of age. The inclusion of broken rice in diet did not have a significant effect on Escherichia coli and Bifidobacteria counts in ileum or Bifidobacteria, Escherichia coli, and Lactobacillus counts in ceca of 10 d old broiler chickens. The villus height in duodenum, jejunum and ilium in birds fed diet containing 4.5% ISP and 18% broken rice were increased (P < 0.05) by 6% at 5 and 4% at 10 d of age. It is concluded that, the inclusion of ISP and broken rice in pre-starter diet may have some beneficial effects on gut morphology, and performance of broiler chickens.

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