After the collection of olive leaves from Chattogram region, they were washed, cleaned and air-dried. Then, those were ground by an electric grinder (Panasonic MX-AC555). The probiotics cultures (Lactobacillus plantarum KCTC 3104 and Saccharomyces cerevisiae KCTC 7915) were purchased from the Add Bio Bd Inc., Dhaka Bangladesh. MRS broth (HiMedia Laboratories Pvt. Ltd., India) and YM broth (HiMedia Laboratories Pvt. Ltd., India) used for growth of Lactobacillus plantarum and Saccharomyces cerevisiae respectively as per instructions of the company. For solid state fermentation, deoiled rice bran and distiller’s dried grains with solubles (DDGS) were used as media. 1% of Lactobacillus plantarum KCTC 3104 and 1.0% of Saccharomyces cerevisiae KCTC 7915 were added to the olive leaves and made its moisture content about 40% to make the fermentation process properly by adding adequate distilled water. The mixture was then incubated at 37ºC for 3 days (Incubator model: LGI-150T, Labnics, USA). The formulated probiotics mixtures were air dried for 2 days until the moisture level was less than 15% using a dry oven (Labnics, USA). To determine the concentration of probiotics in OLP, 10-fold serial dilution was performed and then cultured in MRS agar (Hi-media, Ref:M641-500G) and Potato Dextrose agar (Hi-media, Ref:M096-500G) for growth of Lactobacillus Plantarum and Saccharomyces cerevisiae respectively after which the number of colonies was counted by colony counter and expressed as cfu/gm. A total of 160 days old, unsexed Cobb-500 chicks were distributed in to five dietary treatment groups: Control (Basal diet), OLP -1 (Basal diet + 0.4% OLP, DM basis), OLP -2 (Basal diet + 0.8% OLP, DM basis), OLP -3 (Basal diet + 1.2% OLP, DM basis) and OLP -4 (Basal diet + 1.6% OLP, DM basis) having 4 replications with 8 birds in each in a completely randomized design. A maize and soybean meal-based iso-caloric and iso-nitrogenous diet was prepared for both the starter and grower stage according to the nutrient requirements of broiler chickens (NRC, 1994). The starter diets were offered from day 1 to day 14, while grower diets were provided from day 15 to day 28. The proximate composition of dried OLP and basal diet (starter and grower) were determined by the method described by the Association of Official Analytical Chemists (AOAC, 2000). Birds were kept in a close ventilated, wire-floor caged broiler house (90 cm long × 80 cm wide × 40 cm high/cage) at a stocking density of 720 cm2/bird and supplied with ad libitum feed and water throughout the experimental period. The body weight and feed consumption was recorded per pen on a weekly basis from the initial day to the final day of the experiment. Then feed conversion was calculated as feed consumed divided by body weight gain per pen. The breast meat sample was collected and stored at −20°C until analysis. The proximate composition and oxidative rancidity of the meat were determined. For proximate analysis, meat samples were analyzed in triplicate for moisture (934.01), crude ash (942.05), crude protein (988.05), and ether extract (920.39) as described by AOAC (2000). To determine the oxidative stability, meat samples were preserved in a refrigerator at 4°C, after which thiobarbituric acid reactive substance (TBARS) values of meat were assayed when fresh as well as at 1, 2, and 3 weeks according to the modified method described by Du and Ahn (2002). Briefly, 4 g of each sample was mixed with a 10 ml solution composed of 2 M phosphoric acid and 20% trichloroacetic acid. The mixture was then diluted with 10 ml of distilled water and homogenized by homogenizer and filtered through Whatman No. 1 filter paper. Following filtration, 2 ml of the filtrate were transferred to a test tube, after which 2 ml of 2- thiobarbituric acid (0.005 M in DW) was added. The sample test tube was kept in 80 degrees celsius in a hot water bath for 30 min. The absorbance was measured using a Spectrophotometer at 530 nm. TBARS values are expressed as μmol of malondialdehyde (MDA) per 100 g of meat. After collection of blood, serum was separated from which different blood parameters (cholesterol, triglyceride, LDL and HDL) were measured in an automatic analyzer (Humalyzer 300, Merck®, Germany) according to the manufacturer’s instruction (FVMAAU; Addis Ababa, Ethiopia). Cost and return were calculated based on recurrent and fixed cost, while the return was calculated on the sale of birds per unit. Recurrent costs included the cost of bird, labour, feed, medicine, vaccine, electricity and miscellaneous cost. Whereas fixed included housing and equipment cost. Finally net return and BCR was calculated based on total cost and total return. All the data were analyzed following the General Linear Model (GLM) procedure using the Statistics Analysis Systems Institute employing polynomial analysis (version 9.1; SAS Ins. Inc., Cary, NC, USA). Individual cages served as an experimental unit and a group of two birds served as the experimental units for organ weight, meat composition, and oxidative stability. Treatment means were computed with the LSMEANS option of the SAS program and a probability level of p≤0.05 was considered statistically significant.