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.

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.

Effect of sub-lethal concentration of endosulfan on lipid and fatty acid metabolism of spotted murrel, Channa punctatus.

The spotted murrel, Channa punctatuswere exposed to sub-lethal concentration of endosulfan (8.1 microg l(-1)) for 12, 24, 48, 72 and 96 hrto elucidate the impact of pesticide on fatty acid composition of liver and muscle. After endosulfan exposure, fish from each control and experimental tanks were randomly sampled anesthetized, sacrificed and then the liver and muscle were dissected out for lipid and fatty acid (FA) profile. Results showed that total lipid, cholesterol, and triglyceride and FA in liver and muscle, and phospholipid in liver were significantly affected due to pesticide exposure. In liver and muscle tissues, 28.09 and 32.57% reduction of the total lipid, and 42.82 and 49.75% reduction in triglyceride and FAwere observed at the end of 96 hrs of exposure. Reduction of total lipid, triglyceride and FA may be due to their mobilization for energy production to combat stress. In FA, oleic (25.46 to 22.48% in liver and 25.75 to 21.87% in muscle) and linoleic acids (8.04 to 6.83% in liver and 9.88 to 8.09%) were reduced in both the tissues at the end of 96 hr of exposure. It may be concluded that exposure of fish to sub-lethal concentration of endosulfan had influenced the lipid and fatty acid metabolism of Channa punctatus.

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.

Oncological Clearance Following Resection of the Carcinoma Rectum: A Comparison between Laparoscopic and Open Anterior Resection.

Till the day the rectal cancer deaths in the world is in eighth position. For rectal cancer surgery, short-term benefits are expected to be similar for laparoscopic resection of rectum (LRR) and open resection of rectum (ORR). In Bangladesh though the rectal cancer is the sixteenth most common cause of cancer deaths, there is lack of data regarding outcomes of laparoscopic and open surgical approaches for carcinoma rectum. Purpose of study was to compare oncopathological outcomes by quality of surgical resection between LRR and ORR groups. The quasi experimental study was conducted among 46 subjects who attended in the Department of Colorectal Surgery, Bangabandhu Sheikh Mujib Medical University, Bangladesh from July 2020 to June 2021 with rectal adenocarcinoma within 15cm from the anal verge. Equal number of subjects were allocated for LRR and ORR group. Oncopathological end points such as circumferential resection margin (CRM), distal resection margin (DRM), lymph nodes and quality of mesorectal excision were assessed and compared. Here every patients have given their written consent for this study. Mean age of the subjects for LRR and ORR were 45.47±12.66 and 44.47±12.48 years respectively. Majority of the subjects were in age above 40 years (67.0%). The proportion of male (56.5%) were higher than those of female (43.5%). The complete resection was better in LRR (91.3%) than ORR (87.0%) group though statistically not significant. CRM was lower in LRR (0.0%) than ORR (13.0%) group in respect of frequency distribution. DRM was negative for both LRR and ORR group (95.7% each) and it was not statistically significant. ORR met the National Comprehensive Cancer Network (NCCN) criteria of harvesting 12 lymph nodes were as in LRR group 10 lymph nodes were harvested. The mean harvested lymph nodes were 12.2±5.55 and 10.1±5.55 in LRR and ORR group respectively. The study demonstrated that LRR is better (though statistically not significant) in respect of complete resection and CRM while in harvesting lymph nodes, ORR met the NCCN criteria but LRR does not. There is no difference observed regarding DRM in both groups. On oncopathological point of view both the group showed almost equally effective results. Laparoscopic surgery can be opted as the standard operative technique for surgical management of rectal cancer.

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.

Beta-glucan: an ideal immunostimulant in aquaculture (a review).

The major hindrance in the development and sustainability of aquaculture industry is the occurrence of various diseases in the farming systems. Today, preventive and management measures are central concern to overcome such outbreak of diseases. Immunostimulants are considered as an effective tool for enhancing immune status of cultured organisms. Among different immunostimulants used in aquaculture practices, ß-glucan is one of the promising immunostimulant, which is a homopolysaccharide of glucose molecule linked by the glycoside bond. It forms the major constituents of cell wall of some plants, fungi, bacteria, mushroom, yeast, and seaweeds. Major attention on ß-glucan was captivated with the gain in knowledge on its receptors and the mechanism of action. The receptor present inside the animal body recognizes and binds to ß-glucan, which in turn renders the animal with high resistance and enhanced immune response. This review highlights ß-glucan as an immunostimulant, its effective dosages, and route of administration and furthermore provides an outline on role of ß-glucan in enhancing growth, survival, and protection against infectious pathogens pertaining to fishes and shellfishes. Study also summarizes the effect of ß-glucan on its receptors, recognition of proteins, immune-related enzymes, immune-related gene expression and their mechanisms of action.

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.

Alteration in haematological and biochemical parameters of Catla catla exposed to sub-lethal concentration of cypermethrin.

A 60-day experiment was carried out to study the effect of sub-lethal concentration of cypermethrin (1/10th of LC(50)) exposure on haematological and biochemical parameters of the Indian major carp, Catla catla fingerlings. Under exposure, the total erythrocyte count, total leucocyte count, haemoglobin content and haematocrit were decreased. All the studied serum parameters viz. total serum protein, albumin, globulin contents and albumin-globulin ratio were significantly decreased in cypermethrin-exposed fishes. A marked increase was recorded in alanine aminotransferase and aspartate aminotransferase activities in liver, whereas lactate dehydrogenase activity of muscle and acetylcholine esterase activity in brain were inhibited in cypermethrin-exposed fish. The membrane transport enzymes (total adenosine triphosphatase, sodium-potassium adenosine triphosphatase and magnesium adenosine triphosphatase) activities were decreased significantly in the gills of C. catla exposed to sub-lethal concentration of cypermethrin. The present study indicates that sub-lethal exposure of C. catla fingerlings to cypermethrin alters the haematological and biochemical parameters.

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.

High dietary protein combats the stress of Labeo rohita fingerlings exposed to heat shock.

The amelioration effect of high dietary protein against stress was evaluated in Labeo rohita fingerlings, exposed to heat shock. Two hundred and forty fingerlings (6.57 ± 0.04 g, average weight ± SE) were randomly distributed into 4 treatment groups, each with 4 replicates was fed with either of four diets containing different levels of protein (20, 30, 40 or 45%). Water temperatures of all the treatments were within the range of 25.5-26.5°C throughout the experimental period of 30 days. After 30 days of feeding, fish were given heat shock by exposing to 38°C for 2 h. Heat shock significantly decreased (P < 0.05) liver glycogen content in treatment groups fed with 20 and 30% dietary protein, whereas unaffected in the 40 and 45% protein-fed groups. Heat shock significantly increased (P < 0.05) serum glucose and cortisol level in all the treatments. The 40 and 45% dietary protein-fed groups registered significantly higher survival (%) after the heat shock compared with their lower-protein counterparts. Heat shock increased the glycolytic, gluconeogenic, protein metabolic and antioxidative enzymes to cope up with thermal stress. Our results indicate that high-protein diet (≥40%) combats the stress due to heat shock in Labeo rohita.

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.