Ali Abazari - ۱Graduated from Department of Animal Sciences, University of Mohaghegh Ardabili, Ardabil, Iran
Bahman Navidshad - ۲Department of Animal Sciences, University of Mohaghegh Ardabili, Ardabil, Iran
Farzad Mirzaei Aghjehgheshlagh - ۲Department of Animal Sciences, University of Mohaghegh Ardabili, Ardabil, Iran
Saeid Nikbin - ۲Department of Animal Sciences, University of Mohaghegh Ardabili, Ardabil, Iran

Background: There are some reports on the positive effectsof dietary insoluble fiber on the performance of broilers. Objectives: This study was carried out to determine theeffect of inclusion rate and particle size of rice husk in the diet of broilerson the ileal and cecal bacteria populations and small intestine morphology. Methods: The experimental diets  consisted of a control husk-free diet andfour diets containing 7.5 or 15 g/kg rice husk with particle sizes of less than1 mm or between 1-2 mm. Results:The dietary insoluble fiber did not affect feed intake of the experimentalgroups. The best body weight gain and feed conversion ratio was recorded in thebroiler chickens fed the diet containing 15g/kg rice hulls with particle sizeof less than 1 mm (p<0.05). In the duodenum and jejunum, the crypt depth tovilli height ratio in the control group was significantly lower than othergroups (p<0.05). In the ileum, all the birds fed rice husk except the groupfed the diet that contained 15g/kg rice husk with particle size of 1-2 mm,had  higher Lactobacilli and lowerE. coli and coliforms populations than the control group (p<0.05). Conclusions: The results of the present study suggest thatthe 7.5g/kg dietary inclusion and more coarse particles size of rice husk (1-2mm) were more effective to promote broiler growth performance. The positiveeffects of dietary insoluble fiber on the growth performance of broilers inthis study are probably a result of favorable changes in the bacteria populations of the gastrointestinal tract andnot any improvement in small intestine absorptive capacit

Broilers, gut bacteria population, intestine morphology, Particle size, Rice Husk