Physio-metabolic and haematological changes of Labeo rohita fed with graded level of de-oiled rice bran-based diet.

A 60-day feeding trial was conducted with six experimental diets containing 260 g/kg crude protein and 70 g/kg lipid with varying level of de-oiled rice bran (DORB), viz., 33 (T33), 38 (T38), 43 (T43), 48 (T48), 53 (T53) and 58% (T58) to assess the digestive, metabolic and haematological responses in Labeo rohita. One hundred and eighty (180) fingerlings with ten fish per tank having an average weight of 9.8 ± 0.5 g were randomly distributed within six treatments in triplicates following a completely randomised design. The amylase and lipase activities in the whole intestine did not vary significantly (P > 0.05), but protease activity varied significantly with respect to DORB level in the diet. At higher (53 and 58%) inclusion level of DORB, the protease activities were lower. T33, T38 and T43 groups showed significantly (P < 0.05) higher aspartate aminotransferase (AST) activity compared to the other groups, whereas lowest activity was recorded in the group fed with highest inclusion level (58%). The oxidative stress enzyme like superoxide dismutase (SOD), catalase and glutathione-S-transferase exhibited significantly higher activities in liver of T58 group of L. rohita. However, the activity of catalase and SOD showed no significant variation in gill tissue. The haematological parameter values such as red blood cell (RBC), white blood cell (WBC), haemoglobin (Hb) and packed cell volume (PCV) were lower in the highest DORB fed group (T58) as compared to their lower DORB inclusion counterparts. No change in NBT value was recorded irrespective of DORB inclusion level in the diet. Hence, from these results, it can be concluded that the dietary inclusion of DORB up to 43% in the diet of L. rohita at 26% crude protein and 7% lipid level is best for the optimal activity of digestive, metabolic and haematological parameters.

Dietary L-Tryptophan potentiates non-specific immunity in Labeo rohita fingerlings reared under elevated temperature.

At present environmental scenario global climate change is a reality and its affect all living organism including fish. The aquatic ecosystem is the most affected system as it is the biggest sink for global warming and elevated temperature and obviously affects all the aquatic life forms. With this hypothesis an experiment was conducted to evaluate the effect of elevated temperature on Labeo rohita fingerlings and potential of dietary L-tryptophan (TRP) in mitigating the effects elevated temperature and enhancing the non-specific immunity. Seven hundred and twenty fishes were randomly distributed in three different thermal groups each with three replicates. The thermal groups were ambient temperature (26 °C), 34 and 38 °C. Then each thermal groups were fed with four different formulated diets containing 0. 0.36%, 0.72% and 1.44% TRP. The effect of dietary TRP supplementation was studied on stress responses, such as cortisol, blood glucose, histopathological changes in liver and kidney and immuno-hematological changes such as red blood cell count (RBC), haemoglobin (Hb), white blood cell count (WBC), lysozyme, nitroblue tetrazolium (NBT), total serum protein, albumin, globulin and albumin-globulin ratio. Subsequently the treated fish were subjected to challenge test with Aeromonas hydrophila. In the present study, primary stress markers were noticeably (p < 0.01) elevated with temperature stress and levels were reduced with nutritional supplementation of TRP. Similarly, immuno-hematological parameters were altered with the exposure of temeparture stress and got improved with dietary TRP supplementation. Results of the present study suggest that dietary supplementation of 1.44% tryptophan has definitive role in the mitigation of temperature stress and gives protection against bacterial infection to L. rohita.

Haemato-biochemical, non-specific immunity, antioxidant capacity and histopathological changes in Labeo rohita fingerlings fed rubber protein isolate.

A 60-day feeding trial was conducted to evaluate the haemato-biochemical, innate immune response, antioxidant capacity and histopathological changes in Labeo rohita fingerlings fed rubber protein isolates (RPI). One hundred and eighty fingerlings (average weight 4.45 ± 0.01 g) were distributed into five experimental groups in triplicate and fed with isonitrogenous and isocaloric diets. Soybean protein isolate (SPI) served as the reference diet (Control), and the treatment diets were formulated as RPI25, RPI50, RPI75 and RPI100 replacing 25, 50, 75 and 100% of SPI protein, respectively. The growth performance indices like final body weight (9.54-10.27 g), net weight gain (5.09-5.84 g), metabolic growth rate (4.54-5.02) and feed efficiency ratio (0.60-0.65) among the various groups were not significantly different (P > 0.05). All the haematological parameters, except red blood cells, showed no significant differences compared with the control group (P > 0.05). The immuno-biochemical parameters like albumin, globulin, total immunoglobulin, respiratory burst and lysozyme activities among the various groups did not differ significantly (P > 0.05). The stress enzyme such as superoxide dismutase (SOD), catalase (CAT) and oxidative stress marker malondialdehyde (MDA) showed no significant difference (P > 0.05). Histopathological examination of the liver revealed no marked changes. In summary, the results showed that RPI was well utilised by the fish and its inclusion did not generate any oxidative-induced stress, thus, RPI may be suggested as a potential replacement for SPI in fish diets without any detrimental effects. Hence, protein isolation offers a unique opportunity for the utilisation of rubber seed meal.

Dietary protein enhances non-specific immunity, anti-oxidative capability and resistance to Aeromonas hydrophila in Labeo rohita fingerlings pre-exposed to short feed deprivation stress.

Present experiment was conducted to study the effect of dietary protein levels on growth, immunity and anti-oxidative status of Labeo rohita fingerlings during feed deprivation followed by refeeding. Fish (5.44 ± 0.10 g) were deprived of feed for 3 weeks and then re-fed to satiation for 5 weeks with one of the diets containing 25 (25P), 30 (30P), 35 (35P) or 40 (40P) percent crude protein (CP) level. In addition to these groups, a control group (C) was also maintained by feeding to satiation level twice daily with a diet containing 30% CP throughout the experimental period. At the end of 8-weeks' trial, fish were challenged with Aeromonas hydrophila and survival was recorded for the next 7 days. Complete recovery of growth in terms of weight gain percentage was achieved in the fish fed 35 and 40% protein during refeeding. The body indices (condition factor and hepatosomatic index), haematological parameters and serum protein contents at the end of the experimental trial were not significantly different (P > 0.05) among different groups suggesting that the overall health of the fish was not compromised. However, respiratory burst activity and serum lysozyme activity were indicative of a better immune function in the higher protein fed groups (35P and 40P) than the lower protein groups (25P and 30P). Following challenge with Aeromonas hydrophila, survival rate, blood monocyte%, respiratory burst activity, serum lysozyme activity, serum protein and globulin were significantly higher (P < 0.05) in the 35P and 40P groups compared to the other groups. Further, fish fed lower dietary protein were not able to restore the activities of anti-oxidative enzymes (superoxide dismutase and catalase) in the liver. Conclusively, an improved disease resistance capability and immune status was observed in the fish fed a higher dietary protein (35-40%), even out-performing the daily-fed fish.

Mitigation of immunosuppressive and oxidative stress effect of dietary gelatinized starch in Labeo rohita fingerlings by elevation of rearing temperature within optimum range.

The present study was conducted to investigate the strategy to mitigate the immunosuppressive and oxidative stress effect of gelatinized starch in fingerling of Labeo rohita. Fingerlings were either maintained at ambient water temperature (26 °C) or exposed to 32 °C for one week and then subjected to 26 °C for four weeks. Both groups were fed with isoproteinous (30% crude protein) diets containing gelatinized (G) or non-gelatinized (NG) starch. After 5 weeks of feeding trial, fingerlings were challenged by Aeromonas hydrophila and survival rate was recorded for the next 7 days. Serum cortisol and glucose content was significantly (p < 0.05) higher in G starch fed group and decreased with the increase in temperature from 26 to 32 °C, which was consistent for next four week after decrease in temperature from 32 to 26 °C. Lower respiratory burst activity and serum total protein and globulin content in G starch fed group at 26 °C significantly (p < 0.05) increased after elevation of temperature from 26 to 32 °C and levelled off to NG starch fed group. Liver superoxide dismutase (SOD) and catalase (CAT) activity of G starch fed group was significantly higher in group reared at 32 °C compared to 26 °C. After challenge, fish fed G starch showed lower survival rate than that of fish fed NG starch. Subsequently, exposure of elevated temperature (32 °C) for one week significantly increased the survival rate of G starch fed group and levelled off to NG starch fed group. The results of this study indicated that dietary G starch may cause metabolic stress of fingerling L. rohita, as might consequently lead to the decrease antioxidant abilities, depressed immunity and reduced resistance to A. hydrophila infection. Subsequently, exposure of elevated temperature (32 °C) for one week mitigate immunosuppressive and oxidative stress effect of dietary G starch.

Effect of dietary supplementation of l-tryptophan on thermal tolerance and oxygen consumption rate in Cirrhinus mrigala fingerlings under varied stocking density.

A 60 day feeding trial was conducted to study the effect of dietary l-tryptophan on thermal tolerance and oxygen consumption rate of freshwater fish, mrigala, Cirrhinus mrigala reared under ambient temperature at low and high stocking density. Four hundred eighty fingerlings were distributed into eight experimental groups. Four groups each of low density group (10 fishes/75L water) and higher density group (30 fishes/75L water) were fed a diet containing 0, 0.68, 1.36 or 2.72% l-tryptophan in the diet, thus forming eight experimental groups namely, Low density control (LC) (basal feed +0% l-tryptophan); LT1 (basal feed+0.68% l-tryptophan); LT2 (basal feed+1.36% l-tryptophan); LT3 (basal feed+2.72% l-tryptophan); high density control (HC) (basal feed+0% l-tryptophan); HT1 (basal feed+0.68% l-tryptophan); HT2 (basal feed+1.36% l-tryptophan); and HT3 (basal feed+2.72% l-tryptophan) were fed at 3% of the body weight. The test diets having crude protein 34.33±0.23 to 35.81±0.18% and lipid 423.49±1.76 to 425.85±0.31KCal/100g were prepared using purified ingredients. The possible role of dietary l-tryptophan on thermal tolerance and oxygen consumption rate was assessed in terms of critical thermal maxima (CTMax), critical thermal minima (CTMin), lethal thermal maxima (LTMax) and lethal thermal minima (LTMin). The CTMax, CTMin, LTMax and LTMin values were found to be significantly higher (p<0.05) in the treatment groups with CTMax 42.94±0.037 (LT2); LT Max 43.18±0.070 (LT2); CTMin 10.47±0.088 (LT2) and LTMin 9.42±0.062 (LT3), whereas the control group showed a lower tolerance level. The same trend was observed in the high density group (CTMax 42.09±0.066 (LT3); LTMax 43 23±0.067 (HT3); CTMin 10.98±0.040 (HT3) and LTMin 9.74±0.037 (HT3). However, gradual supplementation of dietary l-tryptophan in the diet significantly reduced the oxygen consumption rate in both the low density group (Y=-26.74x+222.4, r²=0.915) and the high density group (Y=-32.96x+296.5, r²=0.8923). Dietary supplementation of l-tryptophan at a level of 1.36% improved the thermal tolerance level and reduced the oxygen consumption rate in C. mrigala fingerlings.

Acclimation of brackish water pearl spot (Etroplus suratensis) to various salinities: relative changes in abundance of branchial Na(+)/K (+)-ATPase and Na (+)/K (+)/2Cl (-) co-transporter in relation to osmoregulatory parameters.

The present study was conducted to elucidate the osmoregulatory ability of the fish pearl spot (Etroplus suratensis) to know the scope of this species for aquaculture under various salinities. Juvenile pearl spot were divided into three groups and acclimated to freshwater (FW), brackish water (BW) or seawater (SW) for 15 days. The fish exhibited effective salinity tolerance under osmotic challenges. Although the plasma osmolality and Na(+), K(+) and Cl(-) levels increased with the increasing salinities, the parameters remained within the physiological range. The muscle water contents were constant among FW-, BW- and SW-acclimated fish. Two Na+/K+-ATPase α-isoforms (NKA α) were expressed in gills during acclimation in FW, BW and SW. Abundance of one isoform was up-regulated in response to seawater acclimation, suggesting its role in ion secretion similar to NKA α1b, while expression of another isoform was simultaneously up-regulated in response to both FW and SW acclimation, suggesting the presence of isoforms switching phenomenon during acclimation to different salinities. Nevertheless, NKA enzyme activities in the gills of the SW and FW individuals were higher (p < 0.05) than in BW counterparts. Immunohistochemistry revealed that Na(+)/K(+)-ATPase immunoreactive (NKA-IR) cells were mainly distributed in the interlamellar region of the gill filaments in FW groups and in the apical portion of the filaments in BW and SW groups. The number of NKA-IR cells in the gills of the FW-acclimated fish was almost similar to that of SW individuals, which exceeded that of the BW individuals. The NKA-IR cells of BW and SW were bigger in size than their FW counterparts. Besides, the relative abundance of branchial Na(+)/K(+)/2Cl(-) co-transporter showed stronger evidence in favor of involvement of this protein in hypo-osmoregulation, requiring ion secretion by the chloride cells. To the best of our knowledge, this is the first study reporting the wide salinity tolerance of E. suratensis involving differential activation of ion transporters and thereby suggesting its potential as candidate for fish farming under different external salinities.

Stress mitigating and growth enhancing effect of dietary tryptophan in rohu (Labeo rohita, Hamilton, 1822) fingerlings.

An experiment was conducted to study the stress mitigation and growth enhancing role of dietary L-tryptophan (TRP) under thermal stress in rohu, Labeo rohita fingerlings for 45 days. Seven hundred and twenty fishes were distributed in three major groups that are ambient temperature (26 °C), 34 and 38 °C in triplicate following a complete randomized design. Acclimation of fishes to 34 and 38 °C over average ambient temperatures were carried out at 1 °C/day. Each group was fed with a diet supplemented with 0, 0.36, 0.72 or 1.42 % L-TRP. Results showed that blood glucose and serum cortisol level were found to be significantly higher (p < 0.05) in the higher temperature groups than the ambient temperature group. Similarly, aminotransferase, lactate dehydrogenase, malate dehydrogenase, CAT, superoxide dismutase activities were found to be significantly higher (p < 0.05) in the control groups (0 % L-TRP) and decreasing activities of these enzymes were observed with the increasing level of dietary L-TRP. In different temperature groups, L-TRP-supplemented groups were found to have higher (p < 0.05) growth, RGR and PER. The results obtained in the present study indicate that dietary L-TRP mitigates thermal stress and enhances growth. From the present study, we can conclude that dietary supplementation of L-TRP at the 0.72 % level in the diet is found to be optimum to reduce thermal stress even up to 38 °C in rohu, L. rohita. The baseline data obtained here could be useful for the farmers to formulate feeds to culture the fish in different agro-climatic zones.

Physiological responses of dietary tryptophan fed Labeo rohita to temperature and salinity stress.

Two experiments were conducted to elucidate the possible effects of dietary L-tryptophan (TRP) in Labeo rohita based on growth performance and physio-biochemical responses. In the experiment I, a 60-day feeding trial was carried out to elucidate the effects of dietary TRP enrichment on growth performance and physio-biochemical responses. In the experiment II, the TRP pre-fed L. rohita, from experiment I, was exposed to temperature and salinity stress to evaluate stress-mitigating efficacy of TRP. In L. rohita, dietary supplementation of TRP showed significant effect on weight gain percentage and feed conversion ratio but not on blood glucose. A significant increase in RNA content and RNA/DNA ratio upon TRP supplementation was observed and was positively correlated with growth performance. The results of experiment II indicated that weight gain percentage, serum T3 and T4 levels were significantly reduced in groups that were exposed to temperature and salinity stress and fed diets without TRP supplementation. However, dietary supplementation of TRP significantly augmented weight gain percentage in stress-exposed groups. Tryptophan supplementation helped in bringing back T3 and T4 levels comparable with control. A significant increase in superoxide dismutase, catalase, Adenosine triphosphatase, blood glucose and serum cortisol was observed in temperature- and salinity-exposed groups fed without TRP-supplemented diets. However, TRP supplementation was found to be effective in restoring the above parameters. The results of these experiments suggest that dietary TRP supplementation augments growth, lowers energy demand and helps in mitigating thermal and salinity stress in L. rohita.

Nitrite-induced alterations in sex steroids and thyroid hormones of Labeo rohita juveniles: effects of dietary vitamin E and L-tryptophan.

An experiment was conducted to study the effect of sub-lethal nitrite exposure on sex steroids (testosterone and estradiol), cortisol and thyroid hormones (T3 and T4) of Labeo rohita juveniles. Fishes previously fed with normal or elevated levels of vitamin E (VE) and tryptophan for 60 days were exposed to sub-lethal nitrite for another 45 days with same feeding regime. There were nine treatment groups, viz. VE0TRP0-N, VE0TRP0+N, VE100TRP0-N, VE100TRP0+N, VE100TRP0.75+N, VE100TRP1.5+N, VE150TRP0+N, VE300TRP0+N and VE200TRP1+N. Except the groups VE0TRP0-N and VE100TRP0-N, all other groups were exposed to nitrite. At the end of the 45 days of nitrite exposure, serum samples were assayed for sex steroids, cortisol and thyroid hormones. The serum T3 and T4 levels decreased to the extent of 84.5 and 94.06%, respectively, upon nitrite exposure. Dietary supplementation with additional amounts of VE and tryptophan appears to reduce the decline of the production of T4. The serum testosterone and estradiol decreased 97.31 and 92.86%, respectively, upon nitrite exposure. Supplementation with additional amounts of VE was found to reverse nitrite-induced inhibition of testosterone and estradiol production. Serum cortisol increased upon nitrite exposure and unexposed (VE100-N) group showed lower levels, which were comparable to groups fed with elevated levels of VE. The overall results of the present study revealed that environmental nitrites have a negative impact on steroidogenesis, which can be overcome by dietary supplementation of elevated amounts of VE (minimum of 150 mg VE Kg diet(-1)) and to a lesser extent by tryptophan (only at the level of 1.5% of the diet).

Thermal tolerance, oxygen consumption and haemato-biochemical variables of Tor putitora juveniles acclimated to five temperatures.

A 30-day acclimation trial was conducted using Tor putitora to elucidate its thermal tolerance, oxygen consumption, haemato-biochemical variables and selected enzymatic activities at five acclimation temperatures (AT). Juveniles of T. putitora were randomly distributed among five treatment groups (20, 23, 26, 29 and 32 ± 0.5 °C). There was a significant curvilinear increase in critical thermal maxima (CT(max)) (y = -0.0693x² + 1.7927x + 34.628, R² = 0.996) and lethal thermal maxima (LT(max)) (y = -0.1493x² + 2.3407x + 35.092, R² = 0.991) with increasing AT. The oxygen consumption rate increased significantly with increasing AT. The Q10 values were 1.16 between 20 and 23 °C, 3.09 between 23 and 26 °C, 1.31 between 26 and 29 °(C) and 1.76 between 29 and 32 °C of AT. The acclimation response ratios were ranged between 0.37 and 0.59. Catalase, superoxide dismutase and ATPase activities were increased linearly in liver, gill and kidney, while brain acetylcholine esterase activity decreased linearly with increasing AT. Blood glucose remained unchanged up to AT of 26 °C and increased significantly at AT of 29 and 32 °C. Haemoglobin content was increased linearly with increasing AT. The highest WBC count was observed at 20 °C, and no significant changes found till AT of 26 °C and significantly decreased at 32 °C. Total serum protein and globulin were significantly decreased with increasing AT. Highest values were observed at 20 °C and remained consistent till 26 °C, then decreased significantly. There was no significant change in A/G ratio through the AT 20-29 °C and increased significantly at 32 °C. The increase in CT(max), LT(max) and oxygen consumption rate with increasing AT may suggest that the thermal tolerance of T. putitora is dependent on its prior thermal exposure history, and it could adapt to higher AT by altering its haemato-biochemical variables.

Supplementation of microbial levan in the diet of Cyprinus carpio fry (Linnaeus, 1758) exposed to sublethal toxicity of fipronil: effect on growth and metabolic responses.

A 60-day feeding trial was conducted to study the effect of dietary microbial levan on growth performance and metabolic responses of Cyprinus carpio fry exposed to sublethal dose (1/10th LC50) of fipronil [(±)-5-amino-1-(2,6-dichloro-α,α,α-trifluoro-p-tolyl)-4-trifluoromethylsulfinylpyrazole-3-carbonitrile]. Two hundred and twenty five fry were randomly distributed in five treatments in triplicates. Four purified diets were prepared with graded levels of microbial levan. Five different treatment groups were levan control L0P0 (basal feed + 0 % levan without exposure to pesticide); pesticide control L0P1 (basal feed + 0 % levan with exposure to pesticide); L0.25P1 (basal feed + 0.25 % levan with exposure to pesticide); L0.50P1 (basal feed + 0.50 % levan with exposure to pesticide); and L0.75P1 (basal feed + 0.75 % levan with exposure to pesticide). Weight gain% and specific growth rate were significantly higher (p < 0.05) in levan fed groups compared to their non-levan fed counterpart. Highest (p < 0.05) content of ascorbic acid in muscle, liver and brain tissues was observed with higher level of dietary levan. Glucose-6-phosphate dehydrogenase activity decreased with the increasing level of dietary levan in the liver and muscle. Aspartate aminotransferase activity exhibited a second order polynomial relationship with the dietary levan, both in liver (Y = -1.001x² + 5.366x + 5.812, r² = 0.887) and muscle (Y = -0.566x² + 2.833x + 6.506, r² = 0.858) while alanine aminotransferase activity showed third order polynomial relationship both in liver (Y = 1.195x³ - 12.30x² + 35.23x + 9.874, r² = 0.879) and muscle (Y = 0.527x³ - 8.429x² + 31.80x + 8.718, r² = 0.990). Highest (p < 0.05) superoxide dismutase activity in gill was observed in the group fed with 0.75 % levan supplemented diet. Overall results indicated that dietary microbial levan at 0.75 % in C. carpio fry ameliorated the negative effects of fipronil and augmented the growth.

Effect of alternate day feeding strategy of sub-optimal protein level on haemato-biochemical responses in Labeo rohita (Hamilton) juveniles.

A feeding trial was conducted for 60 days to delineate the effect of alternate day feeding strategy of sub-optimal protein level on haematological parameters, serum parameters and phagocyte respiratory burst activity (NBT) in Labeo rohita juveniles. One hundred and thirty-five fingerlings (1.87 ± 0.01-2.26 ± 0.05 g) were distributed in triplicate groups of each treatment, and fish were fed at 5% body weight daily. Three experimental isocaloric (401.32-410.28 kcal/100 g) diets of 30%, 25%, and 20% crude protein designated as diet A, diet B, and diet C respectively, were prepared, using locally available feed ingredients. Three different feeding schedules of normal protein diet continuously (diet A-30%), alternate feeding of 1-day diet A followed by 1-day diet B (1A/1B) and alternate feeding of 1-day diet A followed by 1-day diet C (1A/1C) were tested. The total erythrocyte count and haemoglobin content was significantly (p < 0.05) enhanced in the group T1 fed (1A/1B), and the lowest count was recorded in the group T2 fed (1A/1C). Total leucocyte counts, total serum protein, and serum globulin were higher in the group T1 fed (1A/1B) and lower in the group T2 fed (1A/1C) as compare to control. The respiratory burst activity (NBT) of blood phagocytes and serum A-to-G ratio was recorded significantly difference in among the treatment groups. Based on the results of the present study, it is concluded that alternate feeding of 1-day diet A followed by 1-day diet B (1A/1B) is equally effective and promote the immunity in Labeo rohita juveniles.

Effects of dietary pyridoxine on haemato-immunological responses of Labeo rohita fingerlings reared at higher water temperature.

A sixty-day feeding trial was carried out to elucidate the effect of dietary pyridoxine (PN) on hemato-immunological parameters in Labeo rohita fingerlings exposed to an elevated temperature (ET) of 33 °C. Two hundred and seventy fingerlings (6.71 ± 0.32 g) were randomly distributed into six treatments in triplicates (15 fish/tank). Five iso-nitrogenous (356.3 ± 2.7 g/kg crude protein) purified diets were prepared with graded levels (0, 10, 50, 100 and 200 mg/kg diet) of PN. Six treatment groups were P10T26 (10 mg PN + ambient temperature (26 °C), P0T33 (0 mg PN + ET), P10T33 (10 mg PN + ET), P50T33 (50 mg PN + ET), P100T33 (100 mg PN + ET) and P200T33 (200 mg PN + ET). The responses of L. rohita fingerlings to dietary PN were assessed in terms of growth and by analysing some hemato-immunological parameters. When PN supplementation increased from 10 to 200 mg/kg diet, a significant improvement in weight gain percentage was observed. Erythrocyte (RBC) count, leucocyte (WBC) count, haemoglobin content and respiratory burst activity were significantly (p < 0.05) higher in 100 mg PN/kg diet-fed group than their non-PN-fed counterpart. Also, serum albumin, globulin and lysozyme activity were found significantly (p < 0.05) higher in PN-fed groups. The overall results indicated that dietary PN supplementation at 100 mg/kg diet may reverse the negative effects caused by ET and may protect the haemato-immunological status of L. rohita fingerlings reared at higher water temperature.

Alterations in serum electrolytes, antioxidative enzymes and haematological parameters of Labeo rohita on short-term exposure to sublethal dose of nitrite.

An experiment was conducted to study the effects of short-term exposure to sublethal levels of nitrite on electrolyte regulation, antioxidative enzymes and haematological parameters in Labeo rohita juveniles. The fishes were exposed to graded levels of nitrite (0-15 mg l(-1)) for different duration (0, 12, 24, 48 and 96 h). The 96-h LC(50) value for L. rohita (avg. wt, 66.5 ± 0.5 g) was found to be 11.28 mg l(-1). Activities of antioxidative enzymes (catalase and superoxide dismutase), acetylcholine esterase (AChE) and methaemoglobin reductase, serum electrolytes (sodium, potassium and chloride), haematological parameters and blood glucose level significantly varied (P < 0.05) in a dose-dependent manner. With increasing nitrite concentration and exposure period, a progressive reduction in the total erythrocyte count and haemoglobin were observed. With increase in nitrite concentration, a significant (P < 0.05) increase in activities was evidenced in catalase and superoxide dismutase in liver as well as gill, methaemoglobin reductase in blood, while progressive decline in AChE activity in brain was recorded. The serum sodium and chloride content showed a progressive decline, while potassium showed an increasing trend upon increase in nitrite concentration. The serum K(+) and Cl(-) after 96-h exposure demonstrated a linear relationship (Y = 0.221x + 2.542, R (2) = 0.938, P < 0.01 and Y = -5.760x + 129.5, R (2) = 0.952, P < 0.01, respectively) with nitrite concentrations. This study revealed that nitrite exposure causes alteration in all measured tissue enzymes, serum electrolytes and haematological parameters.

Water soaking and exogenous enzyme treatment of plant-based diets: effect on growth performance, whole-body composition, and digestive enzyme activities of rohu, Labeo rohita (Hamilton), fingerlings.

A 2 × 2 × 2 factorial experiment was conducted to delineate the main effect of water soaking of plant ingredients, phytase, cellulase, and their interactions on the growth and digestive enzyme activities of Labeo rohita fingerlings. Two basal diets were prepared using water-soaked (S) or unsoaked (US) plant-based ingredients. Feed of US ingredients was supplemented with phytase (U kg(-1)) and cellulase (%) at the level of 0, 0 (C(us)); 500, 0 (T(1)); 0, 0.2 (T(2)); 500, 0.2 (T(3)), and feed of S ingredients at 0, 0 (C(s)); 500, 0 (T(4)); 0, 0.2 (T(5)), and 500, 0.2 (T(6)), respectively. Three hundred and sixty fingerlings were randomly distributed into eight treatments, each with three replicates. Soaking of the ingredients for 24 h significantly reduced the tannin content. However, feeding of S diets did not improve the fish growth. Highest performance was recorded in the T(3) group. A significant interaction between dietary phytase and cellulase was observed for apparent net protein utilization. Tissue crude protein, ether extract, and ash content of the fingerlings were observed highest in the T(3) group. Activities of amylase, protease, and lipase were recorded highest in the T(3) group. Results suggested that soaking of plant-based ingredients reduces tannin content; however, growth and digestive enzyme activities of group fed soaked diet were not improved, possibly due to leaching of soluble nutrients. Probably, a shorter duration soaking may be effective in reducing tannin content and avoiding nutrients leaching.

Acute and chronic effects of endosulfan on the haemato-immunological and histopathological responses of a threatened freshwater fish, spotted murrel, Channa punctatus.

Two experiments, one short-term and one long-term, were conducted to elucidate the acute and chronic effects, respectively, of endosulfan exposure on the haemato-immunological and histopathological responses of Channa puncatatus. In the short-term study, fish were exposed to sublethal endosulfan (8.1 µg l(-1)) for 12, 24, 36, 48, 72 and 96 h. In the long-term study, fish were fed with normal diet and simultaneously either exposed to endosulfan (1.2 µg l(-1)) for 90 days or not. Results showed that the ascorbic acid levels in both the liver and the muscle decreased significantly (P < 0.05) by acute and chronic endosulfan exposure. The haemoglobin (Hb) level reduced significantly (P < 0.05) by 15.5% within 12 h of acute endosulfan exposure, further decreased by 25.8% after 24 h of exposure, however, thereafter the values increased and at the end of 72 h returned to normal levels. Almost similar trend was observed for the erythrocyte (RBC) count. The WBC count and the nitroblue tetrazolium (NBT) value showed a general increasing trend with increase in the duration of acute endosulfan exposure. The chronic exposure of C. punctatus to endosulfan significantly (P < 0.05) lowered the Hb level, RBC and WBC counts, NBT reduction value and the plasma parameters such as plasma protein, albumin (A) and globulin (G) compared with that of the control (except for A/G ratio). Endosulfan exposure also severely altered the liver histological structure. Overall results indicated that both short-term acute and long-term chronic endosulfan exposure had a significant impact on the haemato-immunological parameters and tissue histopathology of C. punctatus.

Haemato-immunological and stress responses of Labeo rohita (Hamilton) fingerlings: effect of rearing temperature and dietary gelatinized carbohydrate.

A feeding trial of 70-days was carried out to study the haemato-immunological and stress responses of Labeo rohita fingerlings reared at two water temperatures [ambient (Amb) - 27 °C and 32 °C] fed with graded levels of gelatinized corn carbohydrate (GC). Two hundred and sixteen fingerlings were randomly distributed into six treatment groups in triplicate. Three semi-purified diets were prepared containing 30% crude protein with graded levels of GC 40%, 50% and 58%. The six treatment groups were T(1) (40% GC × Amb), T(2) (40% GC × 32 °C), T(3) (50% GC × Amb), T(4) (50% GC× 32 °C), T(5) (58% GC × Amb) and T(6) (58% GC × 32 °C). The blood glucose level was significantly (p < 0.05) lowered in groups fed with 58% GC level. Neither dietary GC levels nor temperature had a significant (p > 0.05) effect on serum cortisol and superoxide dismutase activity. Lysozyme activity was significantly higher (p < 0.05) in T(1) during pre- and post-challenge period while temperature alone had a significant (p < 0.05) effect on post-challenge Nitroblue Tetrazolium and found higher at 32 °C. A significant effect of GC levels and rearing temperature was recorded on WBC in the pre- and post-challenge period. Highest pre-challenge WBC was observed in T(4) group and in the post-challenge period T(1) group recorded maximum. Water temperature had significant effect on pre-challenge haemoglobin content, highest being at 32 °C (T(2) ). A significant (p < 0.05) effect of rearing temperature and dietary GC level on total serum protein and albumin was also observed. Highest total serum protein and albumin was recorded in T(1) and globulin in T(2) . Percentage survival after challenging with Aeromonas hydrophila was highest in T(1) followed by T(3) group and lowest in T(6) . The results obtained in the present study suggest that L. rohita fingerlings may utilize higher levels of dietary GC at higher temperature (32 °C) but may affect its immunity status.

Higher water temperature enhances dietary carbohydrate utilization and growth performance in Labeo rohita (Hamilton) fingerlings.

A 60-day experiment was conducted to delineate the effect of three dietary levels of gelatinized carbohydrate (GC) on growth, nutrient-utilization and body composition of Labeo rohita fingerlings (avg. wt 6.5 ± 0.3 g) reared at two water temperatures (ambient-AT (26 ± 0.8 °C) and 32 °C). Two hundred and sixteen fingerlings were randomly distributed into six treatments in triplicates. Three semi-purified isonitrogenous diets were prepared with graded levels of GC viz. D(1) : 40%, D(2) : 50% and D(3) : 58%. Growth rate, feed efficiency and protein efficiency ratio were significantly (p < 0.05) higher in 50% GC and 32 °C reared groups than their AT counterparts. Hepato Somatic Index was higher in AT reared groups compared to 32 °C reared counterparts. Apparent digestibility co-efficient of carbohydrate was significantly (p < 0.05) higher at 32 °C reared groups but decreased with increasing carbohydrate (GC) levels. Fish reared at 32 °C showed significantly (p < 0.05) higher amylase, protease and hexokinase activities while glucose-6-phosphate dehydrogenase and glucose-6-phosphatse were significantly (p < 0.05) higher at ambient temperatures. The results obtained in present study indicated that L. rohita could utilize higher level (50%) of dietary carbohydrate at 32 °C.

Haemato-immunology and histo-architectural changes in Labeo rohita fingerlings: effect of dietary aflatoxin and mould inhibitor.

A feeding trail of 60 days was conducted for delineating the effect of dietary aflatoxin (AFB1) with or without supplementation of a mixture of mould inhibitor (0.25% clove oil + 0.32% sodium propionate) on haematology, respiratory burst activity and histology of Labeo rohita fingerlings. Three hundred and sixty fishes (avg. wt. 1.48-1.54 g) were randomly distributed into eight treatment groups. Eight experimental diets with four different levels of aflatoxin (0, 10, 20 and 40 ppb) with or without mould inhibitor were prepared. Haematological parameters like total serum protein, albumin, globulin and A:G ratio were significantly (P < 0.05) reduced with increasing levels of aflatoxin in the diet. However, supplementation of mould inhibitor showed enhanced values when compared to non-supplemented counter parts suggesting ameliorating effects of mould inhibitor on aflatoxin. Total leucocyte count was higher in aflatoxin-treated groups. Histological observations were complementary to haematological parameters. Respiratory burst activity was significantly (P < 0.05) decreased in higher aflatoxin-treated groups but not affected significantly (P > 0.05) due to inclusion of inhibitor alone and/or interaction of aflatoxin level and inhibitor in the diet. From this study, it was concluded that up to 20 ppb aflatoxin level in the diet the haemato-immunological parameters are protected.