Effects of fiber source with various particle size and carbohydrase enzyme on growth criteria, carcass and blood characteristics, digestive enzyme activity, cecal microbial population and ileal morphology of chukar partridge were evaluated for a total period of 90 days. 300 day-old partridge were randomly allotted to a 5 × 2 factorial arrangement with 4 different fiber inclusion with different mean particle size (MPS) (none; rice hulls (RH) (711±1.8 μm); wheat straw (WS) Coarse (3211±1.2 μm); wheat straw Fine (755±1.9 μm); and wheat bran (WB) (767±1.8 μm)) along with a low-fiber control diets and two levels of carbohydrase enzyme (0 or 50 mg/kg). There were 10 treatments and 5 pens with 6 partridge chicks per each treatment. The results indicated that fiber inclusion regardless of fiber source significantly increased body weight (BW) of birds during the whole experimental period (P<0.01). Among the fiber sources, the highest BW attained when fine WS and WB was incorporated into the low fiber diet (P<0.01). The effect of enzyme on body weight was significant on days 60 and 90. Moreover, there were interactive effects (P < 0.01) between fiber sources and enzyme on BW during the trial. Feed intake significantly (P < 0.001) increased at starter (30 days) phase of trial by inclusion of fiber to control diet, but no significant differences were noted after on days 60 and 90. Enzyme addition had no effect on feed intake and also no interactive effect was observed between fiber source and enzyme for feed intake. Feed conversion ratio (FCR) was reduced by inclusion of fiber into control low fiber diet especially at late stage of rearing period (P < 0.05). Plasma uric acid concentration was reduced by inclusion of fiber on day 28 (P < 0.05). Inclusion of fine WS increased plasma triglyceride and very low-density lipoprotein cholesterol (VLDL-C) concentration on day 90 (P < 0.05). There were interactive effects (P < 0.05) between fiber sources and enzyme on total cholesterol a
