Biometric Indices, Physio-Metabolic Responses and Carcass Quality in Rohu (Labeo rohita) during Feed Deprivation.

Understanding changes in biometric indices and metabolism in fish exposed to feed deprivation may be useful in aquaculture. The present study elucidates the effect of feed deprivation on physio-biochemical responses, such as changes in biometric indices, nutrient mobilization patterns, and enzyme activities in rohu (Labeo rohita). Experimental fish (av. wt. 3.41 ± 0.07 g) were deprived of feed and sampled at intervals of 0, 15, 30, 45, and 60 days to measure weight, length, body composition, and the activities of enzymes involved in digestion, metabolism, and antioxidation. A decrease in body weight, condition factor (CF), hepatosomatic index (HSI), and gastrosomatic index (GSI) was observed during the initial stage of feed deprivation (15 to 30 days) but remained unchanged thereafter. The total carbohydrate and lipid content also decreased rapidly up until 30 days, then stabilized. However, the reduction in tissue protein content (% wet weight) continued gradually with the duration of feed deprivation from 12.85 ± 0.36 at 0 days to 10.04 ± 0.67 at 15 days, 8.79 ± 0.59 at 30 days, 6.95 ± 0.69 at 45 days, and 6.16 ± 0.8 at 60 days, which was lower, compared to the other two body constituents. Amylase, protease. and lipase activities significantly reduced up until 30 days, but then stabilized. Although G6PDH enzyme activity decreased, gluconeogenic (LDH, AST, and ALT) and antioxidative (SOD and catalase) enzyme activities increased during initial feed deprivation (up to 30 days). A tissue-specific difference in amino acid metabolism with a major role of ALT in liver and AST in muscle was observed. This study revealed that rohu fingerlings adapted well to feed deprivation up until 30 days, beyond which there was an overall deterioration in the metabolic functions.

Metabolic and cellular stress responses of catfish, Horabagrus brachysoma (Günther) acclimated to increasing temperatures.

We investigated the metabolic and cellular stress responses in an endemic catfish Horabagrus brachysoma acclimated to ambient (26°C), 31, 33 and 36°C for 30 days. After acclimation, fish were sampled to investigate changes in the levels of blood glucose, tissue glycogen and ascorbic acid, activities of enzymes involved in glycolysis (LDH), citric acid cycle (MDH), gluconeogenesis (FBPase and G6Pase), pentose phosphate pathway (G6PDH), protein metabolism (AST and ALT), phosphate metabolism (ACP and ALP) and energy metabolism (ATPase), and HSP70 levels in various tissues. Acclimation to higher temperatures (33 and 36°C) significantly increased activities of LDH, MDH, ALP, ACP, AST, ALT and ATPase and blood glucose levels, whereas decreased the G6PDH enzyme activity and, tissue glycogen and ascorbic acid. Results indicated an overall increase in the carbohydrate, protein and lipid metabolism implying increased metabolic demands for maintaining homeostasis in fish acclimated to higher temperatures (33 and 36°C). We observed tissue specific response of HSP70 in H. brachysoma, with significant increase in gill and liver at 33 and 36°C, and in brain and muscle at 36°C, enabling cellular protection at higher acclimation temperatures. In conclusion, H. brachysoma adjusted metabolic and cellular responses to withstand increased temperatures, however, these responses suggest that the fish was under stress at 33°C or higher temperature.

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.

Lipotropes promote immunobiochemical plasticity and protect fish against low-dose pesticide-induced oxidative stress.

An experiment was conducted to evaluate the role of different lipotropes in modulating immunity and biochemical plasticity under conditions of sublethal low-dose pesticide-induced stress in fish. Labeo rohita fish fingerlings were divided in two sets with one set of fish continuously exposed to low-dose endosulfan (1/10th of 96-h LC50) for 21 days, the other was unexposed, and both sets of fish were fed with practical diets supplemented with either 2 % lecithin, 0.5 % betaine, or 0.1 % choline and compared against unsupplemented diet. Low-dose endosulfan exposure had adverse effects (P < 0.05/P < 0.01) on hematological profile (erythrocyte count, hemoglobin, and hematocrit), serum protein (total protein, albumin, and globulin) and lipid profile (cholesterol and triglyceride), anti-oxidative status (ascorbic acid content of muscle, liver, brain, and kidney and activity of anti-oxidative enzymes: catalase and superoxide dismutase), neurotransmission (acetylcholinesterase activity in muscle and brain), immunological attributes (WBC count, albumin to globulin ratio, phagocytic activity, and serum cortisol), and metabolic plasticity as revealed from enzyme activities (muscle lactate dehydrogenase, liver and kidney glucose-6-phosphatase dehydrogenase-G6PDH activity). Dietary lipotropes prevented these effects completely or partially and the effects were lipotrope dependent. Kinetics (maximum velocity value V max, catalytic efficiency and Michaelis constant K m) of G6PDH enzyme from crude extracts of liver and kidney indicated inhibition due to endosulfan but lipotropes could protect enzyme and showed a stabilizing effect. The supplements also helped maintain integrity of histoarchitecture of the hepatocytes in endosulfan-exposed fish to a great extent. Feeding lipotropes to fish reared in endosulfan-free water also improved hematological and serum protein and lipid profiles and were immunostimulatory. In conclusion, dietary lipotropes, especially betaine and lecithin at the levels used, improve erythropoiesis, serum protein and lipid profile, anti-oxidant status, immunocompetence, neurotransmission, and protect the livers of L. rohita fingerlings even when continuously exposed to low-dose endosulfan.

Effect of dietary carbohydrate on haematology, respiratory burst activity and histological changes in L. rohita juveniles.

A feeding trial was conducted for 60 days to delineate the effect of dietary carbohydrate on the haematology, respiratory burst activity and histology in Labeo rohita juveniles. One hundred and forty four fish (av. wt. 10+/-0.15 g) were randomly distributed into 12 treatment groups with each of two replicates. Twelve semi-purified diets with either 35% or 28% of crude protein were prepared with different amylase concentrations (0, 50, 100 and 150 mgkg(-1)) and starch type (gelatinised, G/non-gelatinised, NG) designated as T1 (NG, 35% CP, 0 mgkg(-1) amylase), T2 (G, 35% CP, 0 mgkg(-1) amylase), T3 (NG, 28% CP, 50 mgkg(-1) amylase), T4 (NG, 35% CP, 50 mgkg(-1) amylase), T5 (G, 28% CP, 50 mgkg(-1) amylase), T6 (G, 35% CP, 50 mgkg(-1) amylase), T7 (NG, 28% CP, 100 mgkg(-1) amylase), T8 (NG, 35% CP, 100 mgkg(-1) amylase), T9 (G, 28% CP, 100 mgkg(-1) amylase), T10 (G, 35% CP, 100 mgkg(-1) amylase), T11 (NG, 28% CP, 150 mgkg(-1) amylase) and T12 (NG, 35% CP, 150 mgkg(-1) amylase). The fish were acclimatised to the experimental conditions for 15 days during which time the control diet was fed. The blood haemoglobin percentage and RBC count was not significantly different (P>0.05) among the various treatments. Highest WBC count, total plasma protein, serum globulin and respiratory burst activity was found at 50 mgkg(-1) dietary amylase supplementation, whereas no variation (P>0.05) was found at 0, 100 and 150 mgkg(-1) dietary amylase supplementation. There was no difference (P>0.05) in the serum albumin and AG ratio among the experimental groups. Feeding either gelatinised or non-gelatinised carbohydrate did not affect the histological structure of the liver, kidney and intestine except in the T4 and T7 groups. The T4 group showed hyperplasia of the intestine and moderate vacuolation in hepatic cells, whereas the T7 group showed hyperplasia of the intestine. Non-gelatinised carbohydrates (46%) along with supplementation with 50 mgkg(-1) amylase stimulated the immune system in L. rohita juveniles. But supplementation of amylase to the gelatinised carbohydrate had no immunostimulating effect.