Efficacy of single and multiple doses of fenbendazole against gill parasites (Dactylogyrus sp.) of Labeo rohita (Hamilton, 1822) and its physio‐metabolic effects on the fish

The study was conducted to investigate the efficacy and physio‐metabolic responses of single and multiple doses of fenbendazole (FBZ) in Labeo rohita against gill parasite (Dacylogyrus sp.). Two Isoenergetic (395 Kcal DE/100 g) and isonitrogenous (35% CP) purified diets viz. control (without FBZ) and treatment (0.2% FBZ) were prepared. The efficacy of FBZ was measured after administration of single dose (20 mg/kg b. wt.) on 0th day and multiple doses of FBZ, that is, 20 mg/kg b. wt. on 0th, 3rd and 7th day through diet. Although oral administration of FBZ at single dose could significantly reduce the parasite in fish in comparison with the control group, 100% efficacy of the drug was not achieved up to 15th day of treatment. On the other hand, multiple doses of FBZ could show almost 100% efficacy on 15th day in terms of elimination of parasites from gill. The drug induced oxidative stress in examined fish. There was no significant change in activities of hepatic and muscle aspartate aminotransferase and alanine aminotransferase of L. rohita up to 15th day after oral administration of FBZ at single dose. But both single and multiple doses of FBZ could significantly enhance the hepatic superoxide dismutase, catalase and glutathione‐S‐transferase activities in fish up to 7th day of drug administration and significantly decreased thereafter up to 15th and/or 30th day. It is concluded that oral administration of FBZ at multiple doses (20 mg/kg b. wt.) on 1st, 3rd and 7th day could be effective against Dactylogyrus sp. infection in L. rohita.     

Haemato‐immunological response of Labeo rohita (Hamilton) fingerlings fed leaf extracts and challenged by Aeromonas hydrophila

A 35 days feeding trial was conducted to assess the haemato‐immunological response of Labeo rohita fingerlings fed ethanolic leaf extracts of Psidium guajava and Mangifera indica, and infected with Aeromonas hydrophila. Six iso‐nitrogenous (354.6–361.6 g kg^?1) purified diets were prepared with graded level of leaf extracts viz., control (basal feed without any extract); TG‐5 (5 g kg^?1 guava extract); TG‐10 (10 g kg^?1 guava extract); TM‐5 (5 g kg^?1 mango extract); TM‐10 (10 g kg^?1 mango extract); and TGM (5 g kg^?1 guava extract +5 g kg^?1 mango extract). Haematological, immunological, biochemical, along with antioxidant enzyme activities were examined after a 35 day‐feeding trial and following a 7 day challenge with A. hydrophila. The haemoglobin, total leucocyte and erythrocyte counts, respiratory burst activity, lysozyme, total protein, albumin and globulin contents increased significantly (P < 0.05) in leaf extracts fed groups compared with the control in pre‐ and post‐challenge conditions. A significant (P < 0.05) decrease was observed in SOD (superoxide dismutase) and catalase activities of the treatment groups compared with the higher value in control. The trends in mortality indicated that groups of fish showing significantly elevated haemato‐immunological responses had the lowest mortality following challenge with A. hydrophila. The results showed that extracts of P. guajava and M. indica appear to be potential immunostimulant at an inclusion level of 5 g kg^?1 in the diet of rohu. But, mixing of both the extract at similar level did not show any synergistic effect, which needs to be tested at its lower level of inclusion.     

Utilization of electron beam irradiated Jatropha kernel meal in the diet of Labeo rohita (Hamilton, 1822) fingerlings

Defatted Jatropha kernel meal (DJKM) was irradiated through electron beam radiation at 25 kGy (IJKM). After irradiation, PEs and phytate were decreased by 36.67% and 55.27%, respectively, with slight reduction in total hydrolysed amino acids in IJKM. A 45‐day feeding trial was conducted to evaluate the utilization of irradiated Jatropha kernel meal (IJKM) in the diet of rohu (Labeo rohita) fingerlings. Five isonitrogenous (300 g/kg CP) and isoenergetic (15 MJ/kg GE) diets such as T0 (control, without IJKM), T5 (50 g/kg IJKM), T10 (100 g/kg IJKM), T15 (150 g/kg IJKM) and T20 (200 g/kg IJKM) were prepared and fed to fish of respective treatments. Fish fed diets containing T15 and T20 groups exhibited significantly lower (p < .05) weight gain, FCE, PER, ANPU, HSI, ISI, survival rate, nutrient and energy digestibility, than the other groups. Fish of higher IJKM fed groups (T15 and T20) also showed lower muscle moisture, protein, ash and higher muscle lipid content. The liver catalase and SOD activities significantly decreased in the higher IJKM fed groups. It is concluded that IJKM (irradiated by 25 kGy electron beam) can be incorporated up to 100 g/kg in carp feed with the replacement of 33% soybean meal and 28% ground nut oil cake without compromising growth performances of Labeo rohita.     

Effects of dietary microbial levan on growth performance,RNA/DNA ratio and some physio‐biochemical responses of Labeo rohita (Hamilton) juveniles

Six isonitrogenous and isocaloric semi‐purified diets were prepared with different levels of microbial levan: control (Basal), T1 (Basal + 2.5 g kg^?1 diet), T2 (Basal + 5 g kg^?1 diet), T3 (Basal + 7.5 g kg^?1 diet), T4 (Basal + 10 g kg^?1 diet) and T5 (Basal + 12.5 g kg^?1 diet), fed to six groups of fish in triplicate tanks. The results of the 60 days feeding trail showed that supplementation of dietary levan significantly affected the weight gain percentage and specific growth rate of the treatment groups fed at 10 g kg^?1 or more levan. Lowest feed conversion ratio (FCR) value and highest survival percentage among levan fed groups were observed with 12.5 g kg^?1 incorporation (T5) and was comparable with (T4) group. Significant increase in muscle RNA level and RNA/DNA ratio was observed with the increasing dietary levan. Fish fed 12.5 g kg^?1 levan had significantly higher protease, amylase and lipase activities compare with the control group. Lowest Aspartate aminotransferase (AST) activity in the liver and muscle was observed in the T5 group fed with highest level of dietary levan. Overall results conclude that dietary microbial levan incorporation at 12.5 g kg^?1 could be used as potent dietary prebiotic for the culture of L. rohita juveniles.     

Nano zinc vis‐à‐vis inorganic Zinc as feed additives: Effects on growth,activity of hepatic enzymes and non‐specific immunity in rohu,Labeo rohita (Hamilton) fingerlings

The effects of dietary administration of inorganic zinc (zinc sulphate, ZnSO₄) and nano zinc (zinc oxide nanoparticles, ZnO‐NP) were evaluated in rohu, Labeo rohita fingerlings. Fish were fed with a basal diet (Control) supplemented with ZnSO₄ (T1, T2 and T3) and ZnO‐NP (T4, T5 and T6) at 10, 20 and 30 mg/kg, respectively, for a duration of 45 days. The results revealed that fish fed diet containing 20 mg ZnO‐NP per kg (T5) had the highest weight gain and specific growth rate (SGR, % per day), which was significantly different (p < .05) from the other experimental diets. Significantly (p < .05), higher activities of the digestive and metabolic enzymes were recorded in the fish fed ZnO‐NP containing diets as compared to the diets containing inorganic Zn or control diet. The maximum serum glucose and protein levels were noted in fish reared on diet T5. Both SGOT and SGPT activities were significantly increased in fish fed Zn‐supplemented diets (T1 to T6), as compared to the control group. Similarly, innate immune parameters were improved with feeding Zn incorporated diets. The highest phagocytic (40.74 ± 0.65%) and respiratory burst (0.33 ± 0.001, OD 630nm) activities were recorded in the fish fed diet containing ZnO‐NPs at 20 mg/kg (T5). The maximum superoxide production and serum peroxidase activity were detected in the fish fed T5 and T6 diets. Overall, results indicated that short‐duration feeding (≤45 days) of dietary ZnO‐NP (20 mg/kg) improved growth, enzyme activity, serum biochemical parameters and immune function in rohu fingerlings.     

Dietary Houttuynia cordata leaf extract and meal enhances the immunity and expression of immune genes in Labeo rohita (Hamilton, 1822)

A feeding trial was conducted to explore the effect of dietary Houttuynia cordata leaf extract (HCLE) and leaf meal (HCLM) on immunological responses and expression of interferon‐gamma (IFN‐γ) and tumour necrosis factor‐alpha (TNF‐α) gene in Labeo rohita fingerlings. Six isonitrogenous (350 g/kg CP) and isocaloric (17 MJ/kg DE) purified experimental diets were formulated with Houttuynia cordata leaf extract and leaf meal comprising control, C (0 g/kg HCLE and HCLM), E2.5 (2.5 g/kg HCLE), E5 (5 g/kg HCLE), E10 (10 g/kg HCLE), M10 (10 g/kg HCLM) and M20 (20 g/kg HCLM). Labeo rohita fingerlings (3.37 ± 0.23 g) were distributed in six experimental groups in triplicates following the complete random distribution. Fish were fed twice daily with respective experimental diets for a period of 60 days. A significantly (p < .05) lower lactate dehydrogenase, malate dehydrogenase, superoxide dismutase and catalase activities were registered in supplemented groups compared with control group, while respiratory burst and lysozyme activities were significantly (p < .05) higher in E10 group compared with other experimental groups. Haemoglobin, total leucocyte count, total erythrocyte count and haematocrit values were significantly (p < .05) higher in E10 group. The expression of IFN‐γ and TNF‐α in both the kidney and liver was significantly up‐regulated in leaf extract and meal supplemented groups with the highest expression in the fish of E10 group. Overall, these results suggest that the dietary supplementation of ethanolic extract of the Houttuynia cordata leaf at 10 g/kg level can enhance the immune response of L. rohita fingerlings.     

Mixed feeding schedule of low and high protein in the diet of Labeo rohita (Hamilton) fingerlings: effect on growth performance,haemato‐immunological and stress responses

Four experimental diets D₁, D₂, D₃ and D₄ having 100, 300, 350 and 400 g protein kg^?1 diet, respectively, were prepared. Fingerlings of Labeo rohita (5.45 ± 0.03 g) were fed with different diets following a mixed feeding schedule with the feeding cycle of 28 days that consisted of either 28 days feeding of diet D₁ or D₂ or 21 days feeding with D₁ diet and 7 days with either D₃ or D₄ diet. Different treatments were T₁ (D₁ for 28 days), T₂ (D₂ for 28 days), T₃ (D₁ for 21 days and D₂ for 7 days), T₄ (D₁ for 21 days and D₃ for 7 days) or T₅ (D₁ for 21 days and D₄ for 7 days). Fingerlings were sampled after three feeding cycles (84 days). Higher (P < 0.05) growth performance and protein utilization efficiency were found in the T₃ group, which was similar to the T₂ group. The blood count, NBT, lysozyme activity, serum parameters and stress indicator parameters also complement for the better immunity in the T₂ and T₃ groups. Therefore, it could be concluded that fingerlings feeding alternately a low‐protein diet (D₁) for 21 days followed by a normal‐protein diet (D₂) for 7 days in a cycle of 28 days for 84 days maintained better growth and health status.     

Nutritional evaluation of fermented Jatropha protein concentrate in Labeo rohita fingerlings

Jatroha protein concentrate (JPC) was prepared by iso‐electric precipitation method. A 45‐day feeding trial was conducted for the nutritional evaluation of JPC and fermented Jatropha protein concentrate (FJPC) in Labeo rohita fingerlings. Seven iso‐nitrogenous (340 g kg^?1 CP) and iso‐energetic (17 MJ kg^?1) diets such as C (soy protein concentrate⁾, T₁ (50 g kg^?1 JPC), T₂ (100 g kg^?1 JPC), T₃ (200 g kg^?1 JPC), T₄ (50 g kg^?1 FJPC), T₅ (100 g kg^?1 FJPC) and T₆ (200 g kg^?1 FJPC) were fed to respective groups. The weight gain % and protein effciency ratio showed a decreasing trend with higher inclusion of JPC whereas these parameters increased gradually on higher inclusion of FJPC. FCR showed the reverse trend. The protease, GOTand GPT activities of FJPC fed groups were significantly higher than their non‐fermented counterparts whereas a reverse trend was observed for LDH and MDH enzyme activities in muscle and liver. The survival rate was 100% in all the treatment groups except for T₂ and T₃. Phorbol esters (PEs) in FJPC was non‐detectable. Results suggested that solid state fermentation with Aspergillus niger is an effective method for removal of PEs and FJPC is a promising protein source in aquafeed.     

Compensatory growth,feed intake and body composition of Labeo rohita fingerlings following feed deprivation

Ten‐week study was performed on Labeo rohita fingerlings (av. wt. 3.75 ± 0.06 g) to investigate the nature of compensatory growth. Fingerlings were deprived of food for 0 (control), 1 (D1), 2 (D2) or 3 (D3) weeks and refed to satiation for 5 weeks. The feed deprivation was carried out in D3 group on week 3, 4 and 5; D2 group on week 4 and 5; D1 group on week 5, and refeeding of all the groups were started from week 6 onwards. The D1 and D2 groups caught up in body weight with that of control fish within 2 weeks and 4 weeks of refeeding, respectively, but the D3 group had significantly (P < 0.05) lower body weight than the control after 5 weeks of refeeding. Higher growth efficiency was observed in all the feed deprived groups in the 1st week of refeeding only. Feed intake in D1 group became similar with the control after 5 weeks of refeeding, but the D2 and D3 groups were still hyperphagic when the experiment terminated. Thus, compensatory growth was due to hyperphagia and improved growth efficiency. In conclusion, complete compensatory growth was observed in L. rohita fingerlings after feed deprivation of 1 and 2 weeks.     

Effects of detoxified Jatropha curcas protein isolate on growth performance,nutrient digestibility and physio‐metabolic response of Labeo rohita fingerlings

Jatropha protein isolate was prepared following the principle of isoelectric precipitation. The isolated protein is low in fibre, lipid and ash, and high in protein and gross energy contents. The antinutritional factors such as phytic acid, tannin and trypsin inhibitor were found to decrease after protein extraction except phorbol esters (PEs), which remain bounded to the protein matrix. Thus, the protein isolate was detoxified and the PEs content reduced significantly. For the feeding trial, six isonitrogenous diets were formulated as DJP 0, DJP 25, DJP 50, DJP 75, DJP 100, or DJP 100 + lysine with detoxified Jatropha protein isolate (DJP) in replacement for soybean protein isolate (SPI) and fed to L. rohita fingerlings (3.25 ± 0.02 g) for 60 days. The weight gain percentage (WG %), specific growth rate and metabolic growth rate values among the groups showed no significant difference (p > .05), except DJP 100 fed group. The feed conversion ratio, protein efficiency ratio, protein productive value, and survival, digestive and hepatic aminotransferase enzymes activities were not significantly affected, whereas intestinal alkaline phosphatase and serum alanine transaminase differ significantly (p < .05). Thus, this study revealed that DJP supplemented with lysine could replace 100% SPI protein without causing any significant effects on fish performance and organ integrity.     

Effect of miconazole nitrate on immunological response and its preventive efficacy in Labeo rohita fingerlings against oomycetes Saprolegnia parasitica

This study evaluated the effect of sublethal doses of antifungal drug miconazole nitrate (MCZ) on immunological responses and its role as a prophylactic drug against S. parasitica in Labeo rohita fingerlings. Fish were fed with sublethal doses of MCZ, that is, T1—6.30 mgMCZ kgBW^?1, T2—12.61 mgMCZ kgBW^?1 and T3—25.22 mgMCZ kgBW^?1, and sampling was done at different time intervals for 240 hr. Immunological parameters viz. lysozyme activity, oxygen radical production and plasma antiprotease activity showed significant enhancement (p < 0.05) in fish fed with T2 and T3 doses. Expression of immune‐relevant genes such as TLR‐22 and β2‐M showed significantly higher expression at 6 hr and 24 hr of sampling in both liver and head kidney. However, these genes showed a downregulation after 120 hr of sampling in both the tissues. Preventive efficacy study showed that single dose of MCZ provides protection against oomycetes up to the fourth day of infection. Significantly higher mortality was observed in control diet‐fed fish as compared to fish fed with MCZ medicated diet. Thus, it can be concluded that the MCZ can act as a potent antifungal agent for preventing oomycetes infection as well as to enhance the immune response.     

Short‐term exposure to higher temperature triggers the metabolic enzyme activities and growth of fish Labeo rohita fed with high‐protein diet

Six hundred Labeo rohita (average weight, 6.78 g) were distributed in 24 tanks (25 fish per tank), which were allotted to eight experimental groups in triplicates. Half of the experimental groups were maintained at ambient water temperature of 26 °C, whereas the other half were exposed to 32 °C for 1 week then later maintained at 26 °C for 4 weeks. Fish reared under different temperature regimes were fed one of the four diets containing 200 g kg^?1, 300 g kg^?1, 400 g kg^?1 or 450 g kg^?1 protein. Growth, feed efficiency and protein retention were higher at 32 °C and continued for the next 2 weeks after decreasing the temperature. The dietary protein level and water temperature interactions were more effective in modulating the response of hepatic glucokinase than that of hexokinase and pyruvate kinase. In contrast, hepatic gluconeogenesis was not affected by rearing temperature. Hepatic aspartate aminotransferase and alanine aminotransferase activity was found higher (P < 0.05) at low temperature and at high protein level. It is suggested that the metabolic activities of fish are triggered by short‐term exposure to higher temperature and the increased metabolic activity extended for a duration of 3 weeks during which 400 g kg^?1 dietary protein level was found to support growth of fish.     

Effect of Ocimum sanctum Linn. (Tulsi) extract on the immunity and survival of Labeo rohita (Hamilton) infected with Aeromonas hydrophila

A 60 days study was conducted to evaluate the efficacy of water extract of Ocimum sanctum Linn. leaf on the immune response and disease resistance of Labeo rohita fingerlings against the Aeromonas hydrophila infection. Ocimum sanctum extract was incorporated in the diets (at 0.0%, 0.05%, 0.1%, 0.2%, 0.5% and 1%) of Labeo rohita, rohu fingerlings (6.6 ± 0.013 g). After 42 days blood, plasma and serum were sampled to determine super oxide anion production, lysozyme activity, total immunoglobulin in plasma, blood glucose, serum total protein, albumin, globulin, albumin:globulin ratio, WBC, RBC, haemoglobin content. Fish were challenged with A. hydrophila after 42 days and mortalities were recorded over 18 days post infection. The results demonstrate enhanced super oxide anion production, lysozyme activity, total immunoglobulin in plasma, serum total protein, globulin, total RBC counts, total WBC counts and haemoglobin content (P < 0.05) in treatments group compared with control group. Dietary O. sanctum extracts of 0.2% showed significantly (P < 0.05) higher protection relative percentage survival (RPS 40.00 ± 5.773%) against A. hydrophila infection than control. These results indicate that O. sanctum leaf extract stimulates the immunity and makes L. rohita more resistant to bacterial infection (A. hydrophila).     

Differential inhibition of digestive proteases by tannin in two size groups of rohu (Labeo rohita,Hamilton): A biochemical and zymography study

This study was intended to evaluate tannin mediated inhibition of digestive proteases in two different size groups (fingerlings, F, 4.5 ± 0.7 cm; advanced fingerlings, AF, 18.2 ± 1.6 cm) of rohu, Labeo rohita. Graded levels (50, 100, 150 and 200 nM) of tannin (Gallotannin, 99% purity) were added to the enzyme extracts (30°C, 1 hr) prior to determination of enzyme activities. Changes in the activity of trypsin, chymotrypsin and total protease in relation to the control sets were determined through biochemical assay of enzymes and SDS‐PAGE zymography. The study revealed that tannin significantly inhibited trypsin, chymotrypsin and total protease activities in a dose dependent manner as evident from the regression equations. The degree of the inhibition appeared to be significantly higher for the F in contrast to the AF (F_5,66 = 282.311; p < 0.0001). Trypsin activities were reduced by 8.04 ± 0.19% to 52.68 ± 0.72% and 5.61 ± 0.22% to 39.46 ± 0.19% in F and AF, respectively. The reduction in Chymotrypsin activities ranged between 16.11 ± 0.03% to 38.02 ± 0.27% in F and 6.31 ± 0.07% to 22.80 ± 0.32% in AF. Total protease activities were reduced by 10.9 ± 0.07% to 49.60 ± 0.32% in L. rohitaF, whereas, it ranged between 5.19 ± 0.06% to 32.60 ± 0.13% in AF. On a comparative scale, the difference in tannin induced inhibition in F and AF were more prominent for trypsin and chymotrypsin than total protease. Further, nine protease activity bands (15.9–69 kD) with different electromobility were noticed in both the size groups. Subsequent densitometry analysis revealed that the average densities of the protease activity bands were gradually decreased with increasing level of tannin exposure (50–200 nM). The study might indicate adaptive tolerance to tannin in larger size groups and emphasizes the need for removal of tannin in the plant feedstuffs, especially for feeding the fingerlings of L. rohita.     

Dietary L‐tryptophan modulates growth and immuno‐metabolic status of Labeo rohita juveniles exposed to nitrite

Effect of nitrite exposure on growth and immuno‐metabolic responses of Labeo rohita fed L‐tryptophan (TRP) was studied. Fish previously fed normal and elevated levels of tryptophan for 60 days were exposed to nitrite (2.0 mg L^?1) for another 45 days with same feeding regime. There were four treatment groups, viz., TRP₀‐N (control), TRP₀+N, TRP_0.75+N (0.75% supplemental tryptophan in the diet) and TRP_1.5+N (1.5% supplemental tryptophan in the diet). Highest weight gain% and SGR were observed in control and lowest in TRP₀+N. Dietary supplementation of elevated levels of tryptophan augmented weight gain% and SGR. Nitrite exposed groups recorded higher catalase, SOD, LDH, AST and ALT activities compared with control. However, activities reduced with additional levels of tryptophan supplementation. Nitrite exposure reduced WBC count, total protein, albumin, globulin and lysozyme activity compared with unexposed group but groups which were fed additional amounts of tryptophan restored total protein, albumin and globulin similar to TRP₀‐N. In conclusion, nitrite exposure had adversely affected growth, increased activities of LDH, AST, ALT, catalase, but decreased WBC, serum protein, lysozyme and acetylcholine esterase activity of L. rohita. Normal requirement of tryptophan was unable to combat nitrite stress. However, dietary fortification with tryptophan (minimum 0.75% of diet + normal requirement) found effective in combating nitrite induced stress.     

The immune response in rohu,Labeo rohita (Actinopterygii: Cyprinidae) to Argulus siamensis (Branchiura: Argulidae) infection: kinetics of immune gene expression and innate immune response

Argulus siamensis is a major pathogen in freshwater aquaculture. The immune responses of Indian major carp, Labeo rohita to experimental infection of A. siamensis was evaluated by quantitation of immune‐relevant gene expression in head kidney and skin, and serum innate immune parameters through the course of infection. In skin of infected fish, antioxidant genes like natural killer cell enhancing factor (NKEF‐B) and superoxide dismutase (MnSOD) were significantly up‐regulated in addition to lysozyme G and β₂ microglobulin (β₂M). Both tumour necrosis factor α (TNFα) and toll‐like receptor 22 (TLR22) genes were significantly down‐regulated in skin during early phases of the infection. Most of the genes exhibited significant down‐regulation in head kidney; immunoglobulin (IgM) and β₂M genes being the exceptions which were significantly up‐regulated at 12 h and 3 days post infection. Most of the innate immune parameters like serum complement activity and ceruloplasmin levels showed significant reduction in infected fish. The observed results are indicative of A. siamensis modulating the immune response of rohu by down‐regulation of many immune factors which may explain the susceptibility of rohu to A. siamensis infection. The interaction of this parasite with the host need to be further explored to understand its pathogenesis.     

Replacement of de‐oiled rice bran by soaked and fermented sweet potato leaf meal: Effect on growth performance,body composition and expression of insulin‐like growth factor 1 in Labeo rohita (Hamilton), fingerlings

A 60‐day feeding trial was conducted to determine the growth performance and expression of insulin‐like growth factor 1 gene (IGF‐I gene) in Labeo rohita fingerlings fed with either raw, soaked or fermented sweet potato leaf meal (SPLM) by completely replacing de‐oiled rice bran (DORB), following a completely randomized design. Seven isonitrogenous (30%) and isocaloric (1.8 MJ/100 g) diets were prepared by replacing DORB with 50% and 100% raw, soaked and fermented sweet potato leaf meal, maintaining DORB‐containing diets as a control. Weight gain %, SGR (specific growth rate) and PER (protein efficiency ratio) were significantly (p < 0.05) higher when 100% DORB was replaced by fermented SPLM in comparison to other treatment groups. The fermented and soaked SPLM‐fed groups had registered with lower FCR value. The expression of growth regulating gene IGF‐I mRNA and RNA/DNA ratio was found to be significantly higher (p < 0.05) in soaked and fermented SPLM‐fed groups. In this study, the body protein and lipid composition did not vary significantly (p > 0.05). Hence, the study concludes that the fermented sweet potato leaf meal using Chaetomium globosum can replace 100% DORB in the diet of Labeo rohita without any detrimental effect on growth performance.     

Carbon sources affect water quality and haemato‐biochemical responses of Labeo rohita in zero‐water exchange biofloc system

Biofloc technology degrades waste into useful resources exploiting microbes and can be used in zero‐water exchange systems. To study the effect of different biofloc systems on haematological and metabolic response of Labeo rohita fingerlings, a 60‐days experiment was conducted using four long lasting carbon sources. Seven hundred and fifty fingerlings having mean weight of 4.80 ± 0.12 g were randomly distributed into 15 tanks (n = 50 per tank). Five experimental groups were set in triplicate; T1 (Tapioca), T2 (Wheat), T3 (Corn) T4 (Sugar bagasse) and control (clear water). In‐situ biofloc was developed in 300 L fibre‐reinforced plastic (FRP) tanks and a C/N ratio of 15 was maintained. Water quality variables indicated ammonia immobilization by heterotrophic bacteria, as the dominant mechanism for the removal of toxic‐nitrogenous compounds in the biofloc systems. Results exhibited significantly higher floc volume (53.33 ± 7.88 ml/L), haemoglobin content (6.61 ± 0.03 g/dl) and total leucocyte count (109.66 ± 0.06 thousand cells/mm³) in tapioca biofloc system. Furthermore, the digestive and anti‐oxidative enzymes activities were also significantly higher in tapioca biofloc system. The lactate dehydrogenase and malate dehydrogenase enzyme assays showed a decreased level in tapioca biofloc system as compared with other biofloc systems and control group. Our observations indicate that tapioca biofloc system could improve the water quality, haematological and anti‐stress responses of L. rohita fingerlings in biofloc systems and thus can effectively replace other carbohydrate sources for the biofloc system.