||This 9-month study extending from March 1, to November, 30, 2012 was conducted to find out the effect of different feed ingredients on growth, haematology and vital organs in juvenile Labeo rohita. The experiment was performed to find out the cost-effective substitutes of fishmeal and their effect on growth, digestive enzymes activity, blood profile, histology of intestine and flesh quality was monitored. To obtain the said objectives the experimental fish, Labeo rohita was subjected through three different research trials. i. A 3-month research trial was conducted to evaluate the effect of different plant/animal origin feed ingredients on growth, feed conversion ratio (FCR) and survival of fingerling Labeo rohita. Fish was fed on fish meal, guar meal, corn gluten meal (30%), soybean meal, sunflower meal, rice polish, cotton seed meal, canola meal and rape seed meal individually. Statistical analysis revealed significant differences (P?0.05) in growth, average weight gain, average length increase and specific growth rate among various ingredients. The highest average weight gain 27.162±6.950g and average length increase 6.153±0.833cm was observed in fish fed on guar meal while same was lowest 5.327±1.067g and 1.858±0.137cm, respectively in fish fed on corn gluten. However, fish showed better FCR values (2.01±0.08) when fed on guar meal while the FCR was very poor (9.57±48) for corn gluten (30%) fed group. The survival rate was highest (100%) for soybean meal fed group and lowest (70%) in canola and rapeseed meal fed group. ii. During second 3-month feeding trial, the effectiveness of individual feed ingredient from either plant or animal origin on growth, body composition, enzymes activity, haematology, histology and flesh quality of Labeo rohita was observed. The experiment was conducted in ten fiber glass tanks having size 12 ft x 4ft x 3 ft (length x width x depth). Single ingredient was considered as an independent treatment, hence guar meal, soybean meal, cotton seed meal and canola meal were considered as an independent treatment and fishmeal which was considered as a superior ingredient due to its ideal nutrient balance served as control. Ten juvenile Labeo rohita having an average weight of 200±2.33 g were harvested indiscriminately from the bulk and stocked in each fiberglass tank. Two tanks were randomly allotted to each treatment and control. Each group received uniform ration @ 4% of total fish biomass twice a day. Results revealed significant differences (P?0.05) in growth, FCR and specific growth rates among treatments. Weight gain was the highest in guar meal fed fish while the lowest on fish meal. Body composition of fish showed slight variations in fat contents with no differences in other nutrients though chemical composition of individual ingredient varies a lot. Minerals specifically Na, Ca, Fe, Zn, and Cu significantly differed (P?0.05) among treatments which might be linked with their variable release in digestive system of fish in the presence of various anti-nutritional factors. For different feed ingredients protease activity varied significantly (P<0.05) between anterior and posterior part of the intestine and also that of whole intestine when compared among various treatment groups. While amylase activity differed significantly when enzyme activity compared from the homogenate of whole intestine but not when compared partly. WBC, RBC, Hct, HB, PROT, ALB and GLOB showed significant (P<0.05) differences for blood samples of the fish fed with different feed ingredients while values of MCV, MCH, MCHC and ESR remained uniform. The feed ingredients differently affected the liver and intestinal cells. No difference was observed when fried fish fed on different ingredients were compared among each other indicating that ingredients with nominal variations in chemical composition do not leave much after effects on fish flesh. iii. Third 3-month trial was conducted to evaluate the effect of plant-animal feed and/or plant by-product based feed on growth, body composition, enzymes activity, haematology, histology and flesh quality of Labeo rohita. Fish fed on rice polish alone served as control (T0). Previously selected potential fish feed ingredients were grouped together with two ingredients in each isocaloric test diet which served as an independent trial during these studies. Group 1(T1) contained guar meal and canola meal, group 2(T2) soybean meal and cotton seed meal, group 3(T3) guar meal and cotton seed meal, group 4(T4) soybean meal and canola meal and group 5(T5) fishmeal and canola meal. Each group including control had two replicates. 12 earthen ponds with uniform area of 0.03 ha each, were randomly stocked with 100 fish (average weight 200±4.43g) in each following standard stocking protocols. All the 12 ponds were then randomly allotted to individual treatment including control group. Experimental fish were fed @ 4% of their wet biomass twice a day except Sundays which was kept open providing fish an opportunity to clean left over feed from the previous day. Better growth rate, food conversion ratio (FCR) and specific growth rate (SGR) in T3 than rest of the treatments including control suggest that guar meal and cotton seed meal is much better option to include in future feed formulations for maximum performance and minimum feed wastage. This preposition will minimize feed providing cleaner and healthy environment to fish ultimately enhancing stocking rate and fish production. Proximate analysis of dried and ground fish samples showed higher protein values in T4, fat in T2, moisture contents in control, dry matter in T1 and ash in T5. Mineral composition of Labeo rohita showed statistically significant (P ? 0.05) differences in Na, Ca, Fe, Zn and Cu content. Amylase concentration showed non-significant differences in anterior, posterior parts and the whole intestine in all the treatment and control ponds except T5 while protease concentrations were statistically significant (?0.05) in anterior and posterior part within the same group as well as among various groups. Enzymatic activity in whole intestine also varied significantly when compared among groups. Haematological parameters viz. WBC, RBC, ALB, GLOB and PROT differed significantly (?0.05) among all the treatments. Disrupted hepatic cords and hepatocytes showing pyknotic nucleus were observed in T1, moderate infiltration of fat vacuoles in T2 and, T4 caused vacuolar and hepatic cord degeneration while fish from T0 were subjected to severe vacuolation in hepatocytes. Non-significant differences in flavor, juiciness, and oiliness of fried fish from all the treatments and control ponds indicated that the sensory attributes of fish flesh were not affected by feeding fish with blend of various ingredients. It is concluded that the response of body organs varies with varying feed stuffs and the feed items have pronounced effect on enzymatic activities, hematological and histological parameters in juvenile Labeo rohita. During present study fish showed comparatively better growth when fed with guar meal as a single feed ingredient or combined with cotton seed meal than the rest of feed ingredients either offered individually or in combinations. The study provides base line information and will help aquaculture nutritionists to formulate cost-effective feeds.