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An experiment was carried out to study the effects of exogenous enzymes (cellulases and proteases), yeast culture and effective micro-organism (EM) culture on feed digestibility and the performance of rabbits fed rice bran rich diets over a period of ten weeks. Twenty four, 8 to 9 weeks old male and female New Zealand White rabbits were allotted to 4 dietary treatments; a basal (control) feed containing 43% rice bran, basal feed supplemented with either enzymes, yeast culture or EM. Individual feed intake, body weight gain, nutrient digestibility, carcass characteristics and feed cost were studied. Sex of the rabbits had no significant (p<0.05) influence on the parameters studied. The control group showed the lowest daily feed intake (104.8 g), body weight gain (12.8 g) and the highest feed/gain ratio (8.20 g/g). The highest daily feed intake (114.3 g), body weight gain (20.42 g) and the lowest feed/gain ratio (5.60) were observed with enzymes. Compared to the control, yeast significantly (p<0.05) improved the feed intake, body weight gain and feed/gain ratio by 4.9, 34.4 and 22.0%, respectively, while EM improved (p<0.05) them by 4.0, 32.6 and 21.6%, respectively. All the additives improved (p<0.05) the digestibility of dry matter, crude protein, crude fiber and energy by 4.9-8.7, 3.6-10.7, 5.9-8.3 and 4.3-6.4%, respectively. Higher weights of pancreas (by 38.5-56.4%) and caecum (by 13.1-26.8%, compared to the control) were recorded with all additives but liver weight was increased only by yeast (24.5%) and enzymes (26.7%). Significantly (p<0.05) higher carcass recovery percentages were observed with enzymes (60.55), yeast (60.47) and EM (56.60) as compared to the control (48.52). Enzymes, yeast and EM reduced (p<0.05) the feed cost per kg live weight by 23.8, 15.9 and 15.5%, respectively. Results revealed that enzymes, yeast culture and EM can be used to improve the feeding value of agro-industrial by-products for rabbits in Sri Lanka and thereby to reduce the feed cost. Under the present feeding system, enzyme supplement was the best.