The experiment was conducted to evaluate the effects of different levels of dried citrus sinensis peel (DCSP) on gastrointestinal microbial population of Ross broilers. Four-handred Ross 308 one-day broilers in a completely randomized design with five treatments (four replicates per treatment and each replicate had 20 chicks) were categorized. Each treatment used regulatory diet including 1.5 and 3 percent (DCSP) in the Base diet and in two periods of 1st-21st day and 1st-42nd days and base diet without any additive for six weeks. Data analysis was performed using SAS software and mean comparison was conducted by Duncan method. The results determined that the mean Lactobacilli in ileum on day 42 was not significantly different (p>0.05). The highest rate was concerned to 3% (DCSP) treatment up to the end of rearing period and the lowest one was related to 1.5% (DCSP) treatment up to the end of rearing period. The results from the mean of lactobacilli in cecum in the day 42 indicated that the mean of treatment was not significantly different (p>0.05).The highest rate was concerned to 3% (DCSP) treatment up to the end of rearing period and the lowest one was related to 1.5% (DCSP) treatment up to day 21.
