Three experiments were conducted to assess the potential of partially replacing dietary soybean meal (SBM) with dried distillery yeast sludge (DYS) and its influence on starter, grower and laying hens’ growth and productive performance. In experiment 1, the influence of varying levels of dried DYS on feed consumption, gut health, immunity, histopathology, mortality and growth performance of starter layer chicks from day-one to 8 weeks of age was examined. Five isonitrogenous (CP 21%) and isocaloric (ME 2800 Kcal/Kg) diets were formulated. The control diet (C) was without DYS, whereas DYS5, DYS10, DYS15 and DYS20 diets had 5, 10, 15 and 20% dried DYS, respectively. The higher (P<0.05) feed intake (FI) was noticed in chicks fed C (1701g) and DYS5 (1685g) diets than those fed DYS10, DYS15 and DYS20 diets. Chicks fed C, DYS5 and DYS10 diets had better growth, immune and gut health status than those fed DYS15 and DYS20 diets. Birds fed DYS15 and DYS20 diets showed pathological lesions. The highest weight gain (603g) was noticed in birds fed DYS5 diet. The best feed conversion ratio (FCR) was noticed in birds fed C (2.77) diet followed by DYS5 (2.79), DYS10 (2.82), DYS15 (3.00) and DYS20 (3.13) diets. The higher antibody titers of newcatle disease (ND) and avian influenza (AI) virus were observed in birds fed C diet followed by DYS5 and DYS10, DYS15 and DYS20 diets. The higher lactobacillus count in birds fed DYS5 (13.39 105 cfu/gram) and DYS10 (6.67 105 cfu/gram) diets were noticed. Increasing dietary dried DYS showed enhanced ill effects in birds. In experiment 2, effect of varying dried dietary DYS concentration on feed consumption, gut health, immunity, histopathology, mortality and growth performance of grower layer chicks from weeks 9 to 16 of age was examined. Five isocaloric (ME 2700 Kcal/Kg) and isonitrogenous (CP 16%) experimental diets were formulated. The feed consumption remained unaltered among birds fed C (3248g), DYS5 (3211g), DYS10 (3183g) and DYS15 (3163g) diets. The weight gained by birds fed C (535g), DYS5 (525g) and DYS10 (517g) diets was unchanged. The best feed conversion ratio was found in chicks fed C (6.07) DYS5 (6.12) and DYS10 (6.16) diets than those fed DYS15 and DYS20 diets. The better immune response was observed in chicks fed low dietary DYS than those fed high dietary DYS.A higher lactobacillus count was found in birds fed C (13.40 105 cfu/gram) and DYS5 (13.37 105 cfu/gram) diets. However, it was the lowest (6.50 105 cfu/gram) in birds fed DYS20 diets. The pronounced histological changes were noticed among birds reared on high dietary DYS concentration. In experiment 3, influence of varying dried dietary DYS concentration on feed consumption, gut health, immunity, histopathology, mortality, hematology and hormone profile, egg producrion and its quality in laying hens kept on cage and floor production systems was studied. Five isocaloric (ME 2800 Kcal/Kg) and isonitrogenous (CP 17%) experimental diets were formulated. The FI between cage and floor system remained almost similar. However, the highest feed consumption was noticed in birds fed C diet in cage (11768g) and floor (11799g) production systems and it was the lowest in birds fed DYS diets both in cage and floor production systems. Increasing rate of DYS supplementation in laying hens diet decreased FI. However, FI by hens fed C, DYS5 and DYS10 diets remained unaltered (P>0.05). Similarly hens fed DYS15 and DYS20 diets showed similar (P>0.05) FI in both production sytems. The more eggs per bird were produced by layers fed C diet and they also laid higher eggs both in cage (94) and floor (91) production systems. However, egg production decreased in birds fed increasing dietary DYS concentrations kept under both production sytems. The FCR (calculated per dozen eggs or on egg mass basis) of diets containing varying dietary DYS concentrations remained unaltered in layers kept under both cage and floor production system. The better FCR was found in birds fed C diet and was the lowest in birds fed DYS20 diet. The FCR in birds fed C and DYS5 diets remained unaltered (P>0.05) when compared to those fed DYS10, DYS15 and DYS20 diets. However, increasing dietary DYS concentration reduced FCR in layers. The highest mortality was observed in birds fed DYS20 diet and it was the lowest in those fed C and DYS5 diets but increasing dietary DYS increased mortality in laying hens reared under both cage and floor production systems. The egg weight was higher (P>0.05) in caged hens (62.31g) than those kept on floor (60.27g) production system. The higher egg weight was recored in birds fed C diet and it was the lowest in birds fed DYS20 dietin both cage and floor production systems. The egg weight decreased in birds fed increasing dietary DYS. The egg shell weight and its thickness remained unaltered in both cage and floor production systems. The egg shell weight and its thickness was more in birds fed C diet and it decreased with increasing dietary DYS. The egg shell weight in layers fed DYS20 diet was the lowest among all dietary treatments. The egg’s albumin height was greater birds fed C diet in cages (8.47 mm) and floor (8.35 mm). However, it gradually decreased with increasing dietary DYS. The higher haugh unit score was observed in birds fed C diet in both production systems while it was the lowest in birds fed DYS20 diet. The increased dietary DYS gradually lowered haugh unit score. The lymphocyte and RBCs count were higher in layers fed C diet reared under cage and floor production system but it decreased in birds fed DYS20 diet. The highest Lactobacillus countwas observed in birds fed C (13.25 105cfu/gram) dietand was the lowest in birds fed DYS20 (5.87 105cfu/gram) The increasing dietary DYS reduced Lactobacillus count. The maximum cumulative mean antibody titers against ND were observed in birds fed C diet and was the lowest in birds fed DYS20 diet. The gradual increasing dietary DYS reduced antibody titers in layers. The T3 and T4 hormone values in birds kept under both cage and floor production systems were same, indicating that birds did not experience any kind of stress because of cage and floor production systems. The birds fed DYS10 diet showed highest concentration of T3 hormone (3.96 ng/ml) and it was the lowest (3.88 ng/ml) in birds fed C diet. The gradual increase of DYS supplementation reduced the feed cost per kg during the starter grower and laying phases of production. The highest feed cost was observed in birds fed C diet but it was lowest in chicks fed DYS20 diet. In conclusion, DYS level upto to 10% can be used to replace SBM in poultry diet on protein equivalent basis.