N. P. Sahu

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 32xa0±xa00.5xa0°C). There was a significant curvilinear increase in critical thermal maxima (CTmax) (yxa0=xa0−0.0693x2xa0+xa01.7927xxa0+xa034.628, R2xa0=xa00.996) and lethal thermal maxima (LTmax) (yxa0=xa0−0.1493x2xa0+xa02.3407xxa0+xa035.092, R2xa0=xa00.991) with increasing AT. The oxygen consumption rate increased significantly with increasing AT. The Q10 values were 1.16 between 20 and 23xa0°C, 3.09 between 23 and 26xa0°C, 1.31 between 26 and 29xa0°C and 1.76 between 29 and 32xa0°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 26xa0°C and increased significantly at AT of 29 and 32xa0°C. Haemoglobin content was increased linearly with increasing AT. The highest WBC count was observed at 20xa0°C, and no significant changes found till AT of 26xa0°C and significantly decreased at 32xa0°C. Total serum protein and globulin were significantly decreased with increasing AT. Highest values were observed at 20xa0°C and remained consistent till 26xa0°C, then decreased significantly. There was no significant change in A/G ratio through the AT 20–29xa0°C and increased significantly at 32xa0°C. The increase in CTmax, LTmax 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.

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.xa0rohita, from experiment I, was exposed to temperature and salinity stress to evaluate stress-mitigating efficacy of TRP. In L.xa0rohita, 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.xa0rohita.

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.

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 60xa0days were exposed to sub-lethal nitrite for another 45xa0days 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 45xa0days 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 94.06xa0%, 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 92.86xa0%, 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 150xa0mg VExa0Kg diet−1) and to a lesser extent by tryptophan (only at the level of 1.5xa0% of the diet).

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 feedxa0+xa00xa0% levan without exposure to pesticide); pesticide control L0P1 (basal feedxa0+xa00xa0% levan with exposure to pesticide); L0.25P1 (basal feedxa0+xa00.25xa0% levan with exposure to pesticide); L0.50P1 (basal feedxa0+xa00.50xa0% levan with exposure to pesticide); and L0.75P1 (basal feedxa0+xa00.75xa0% levan with exposure to pesticide). Weight gain% and specific growth rate were significantly higher (pxa0<xa00.05) in levan fed groups compared to their non-levan fed counterpart. Highest (pxa0<xa00.05) 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 (Yxa0=xa0−1.001x2xa0+xa05.366xxa0+xa05.812, r2xa0=xa00.887) and muscle (Yxa0=xa0−0.566x2xa0+xa02.833xxa0+xa06.506, r2xa0=xa00.858) while alanine aminotransferase activity showed third order polynomial relationship both in liver (Yxa0=xa01.195x3xa0−xa012.30x2xa0+xa035.23xxa0+xa09.874, r2xa0=xa00.879) and muscle (Yxa0=xa00.527x3xa0−xa08.429x2xa0+xa031.80xxa0+xa08.718, r2xa0=xa00.990). Highest (pxa0<xa00.05) superoxide dismutase activity in gill was observed in the group fed with 0.75xa0% levan supplemented diet. Overall results indicated that dietary microbial levan at 0.75xa0% in C. carpio fry ameliorated the negative effects of fipronil and augmented the growth.

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 15xa0days. 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 (pxa0<xa00.05) 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 45xa0days. Seven hundred and twenty fishes were distributed in three major groups that are ambient temperature (26xa0°C), 34 and 38xa0°C in triplicate following a complete randomized design. Acclimation of fishes to 34 and 38xa0°C over average ambient temperatures were carried out at 1xa0°C/day. Each group was fed with a diet supplemented with 0, 0.36, 0.72 or 1.42xa0% l-TRP. Results showed that blood glucose and serum cortisol level were found to be significantly higher (pxa0<xa00.05) 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 (pxa0<xa00.05) in the control groups (0xa0% 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 (pxa0<xa00.05) 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 0.72xa0% level in the diet is found to be optimum to reduce thermal stress even up to 38xa0°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.

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 60u2003days 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 (1.87u2003±u20030.01-2.26u2003±u20030.05u2003g) were distributed in triplicate groups of each treatment, and fish were fed at 5% body weight daily. Three experimental isocaloric (401.32-410.28u2003kcal/100u2003g) 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 (pu2003<u20030.05) 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.

Protein requirement of juvenile striped catfish, Pangasianodon hypophthalmus

A trial was conducted to determine the dietary protein requirement for growth of juvenile striped catfish (Pangasianodon hypophthalmus). Iso-energetic semi-purified diets (~u200919.78xa0MJxa0kg−1) with six levels of protein 20% (T1), 25% (T2), 30% (T3), 35% (T4), 40% (T5), and 45% (T6) were fed to triplicate groups of fish (initial mean weight 4.27 to 4.57xa0g) to satiation twice daily for 60xa0days. Growth, feed conversion, protein utilization, intestinal digestive enzyme activities, and body composition were measured as response variables. Best growth (Pu2009<u20090.05) was observed in fish fed with 40% dietary protein, and second order polynomial regression analysis (yu2009=u2009−u20090.0011x2u2009+u20090.0816xu2009+u20090.0642; R2u2009=u20090.9241; dietary protein levels as independent variable and specific growth rate as dependent variable) gave a protein requirement for growth of 37.1%. A minimum feed conversion ratio (FCRu2009=u20091.38) was found in fish fed with 35% dietary protein. Apparent net protein utilization (ANPU) was found to decrease (from 39.57 to 16.15%), with increasing dietary protein levels (Pu2009<u20090.05). Protease and amylase activities were found to be in opposition to each other, with increasing dietary protein levels. The highest protease (0.59xa0μmol of tyrosine released min−1u2009mg−1 protein) and lowest amylase activities (7.99xa0μmol of maltose released min−1 mg−1 protein) were observed in fish fed with 40% dietary protein (Pu2009<u20090.05); whereas lipase activity (Pu2009>u20090.05) was found to be independent of dietary protein levels. Whole body carcass composition (except ether extract) varied with the dietary protein level, and significant higher values of moisture content (72.31%), crude protein (18.83%), and ash content (4.33%) were observed in the treatment group fed with 40% dietary protein. Hence, it may be concluded that the dietary protein requirement for growth of P. hypophthalmus juveniles is 37.1%.

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 4.45xa0±xa00.01xa0g) 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 (9.54–10.27xa0g), net weight gain (5.09–5.84xa0g), metabolic growth rate (4.54–5.02) and feed efficiency ratio (0.60–0.65) among the various groups were not significantly different (Pxa0>xa00.05). All the haematological parameters, except red blood cells, showed no significant differences compared with the control group (Pxa0>xa00.05). The immuno-biochemical parameters like albumin, globulin, total immunoglobulin, respiratory burst and lysozyme activities among the various groups did not differ significantly (Pxa0>xa00.05). The stress enzyme such as superoxide dismutase (SOD), catalase (CAT) and oxidative stress marker malondialdehyde (MDA) showed no significant difference (Pxa0>xa00.05). 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.