In a completely randomized design with a 3*3 factorial arrangement and 4 replicates in each treatment, a study was conducted to evaluate the effect of three levels of Glycine (Gly) (0.00, 0.25 and 0.50%) and three levels of desiccated ox bile (DOB) (0.00, 0.25 and 0.50%) supplementation on performance, fat digestibility, blood chemistry and ileal digesta viscosity of 360 day-old Ross male broiler chickens fed diets containing 5% tallow for a period of 42 days. The isocaloric and isonitrogenous starter and grower diets were fed ad libitum to chickens from 7-21 and 22-42 days of age, respectively. Feed intake (FI), body weight gain (BWG), and feed conversion ratio (FCR) were measured for starter (7-21d) and grower periods (21-42 days of age). Serum cholesterol (Chol), triglyceride (TG), high density lipoprotein (HDL), low density lipoprotein (LDL) and ileal digesta viscosity were measured at 21 and 42 days of age. Chromic oxide at the rate of 3 g/kg was added to experimental diets to determine fat digestibility at 19-21 and 40-42 days of age. FI, BWG and FCR were not affected by dietary treatments during 7-21d of age. Increasing the level of DOB in the diet significantly (P < 0.05) increased FI and BWG, and decreased FCR during 22-42 and 7-42d of age. A linear increase in fat digestibility with DOB was observed (P < 0.05). No significant difference in blood chemistry among birds fed diet supplemented with Gly during starter (7-21d) and grower (22-42d) periods was seen. However, supplementation of 0.50% DOB significantly (P < 0.05) increased Chol, TG, HDL and LDL concentration. Supplementation of Gly with/without DOB in the diets had no effect on the ileal digesta viscosity. The results of this study indicated that supplementation of DOB in the diet significantly (P < 0.05) increased performance and measured blood components. Dietary supplementation of Gly and DOB linearly (P < 0.05) increased fat digestibility of diets containing 5% tallow.

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