Fructooligosaccharide and Bacillus subtilis synbiotic combination promoted disease resistance, but not growth performance, is additive in fish

Species diversification from major to minor carps for their sturdiness and initial higher growth, and also a quest for antibiotic-free aqua farming in the subcontinent, mandates search for and evaluation of alternatives. An experiment was performed to investigate the potential of fructooligosaccharide (FOS) and Bacillus subtilis (BS) (alone or as synbiotics) in promoting growth and immunity against infections in Labeo fimbriatus fingerlings. Six iso-nitrogenous and iso-lipidic diets containing combinations of two levels of FOS (0% and 0.5%) and three levels of BS (0, 104, 106 CFU/g feed) were fed to fish for 60 days. At the end of the feeding trial, twenty-four fish from each group were injected intra-peritoneally with pathogenic strain of Aeromonas hydrophila O:18 to test the immunoprotective efficacy of the supplements against bacterial infection. BS, but not FOS, significantly improved (P < 0.05) growth and feed utilisation attributes like percentage weight gain (PWG), specific growth rate (SGR) and feed conversion ratio (FCR). There were interactive effects of FOS and BS on PWG, SGR and FCR; however, the effects were not additive in nature. These beneficial effects of BS, alone or in combination with FOS, were corroborated by increased protease activity, microvilli density and diameter and number of goblet cells. Overall beneficial effects of FOS and BS included improved erythrocyte (RBC), hemoglobin (Hb), total protein and globulin levels. Total leucocyte (WBC) count and immunological parameters like respiratory burst activity of leucocytes (NBT reduction), lysozyme activity, albumin: globulin ratio and post-challenge survival were significantly improved by both FOS and BS, and their dietary combination yielded the highest improvement in these parameters. Synergistic effects of FOS and BS as dietary supplements indicate that a combination of 106 CFU/g BS and 0.5% FOS is optimal to improve growth, feed utilisation, immune functions, and disease resistance in L. fimbriatus fingerlings.

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

Simple Summary

Feed deprivation is common among animals, including the aquatic animals. Because of this phenomenon, organisms may even suffer from severe metabolic disorders. In the present study, a rapid depletion in carbohydrate and lipid stores was noted in rohu fish (Labeo rohita), together with an elevation in gluconeogenic and antioxidant enzyme activities and inhibition of lipogenic enzyme activity under a diet-deprived condition. The biometric indices, physio-metabolic responses, and carcass quality in the rohu suggest that feed deprivation beyond 30 days caused an overall reduction in their metabolic activities. This is an interesting study, especially for aquatic habitats and aquatic life which may suffer from natural disasters, climate change impacts, or human activities altering their physio-metabolic functions.

Abstract

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.

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.

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.

Biochemical and stress responses of rohu Labeo rohita and mrigal Cirrhinus mrigala in relation to acclimation temperatures

The biochemical and stress responses of two Indian major carps, rohu Labeo rohita and mrigal Cirrhinus mrigala were studied after acclimating them to four preset temperatures (26, 31, 33 and 36 degrees C) for 30 days. The blood glucose and liver glycogen levels showed an inverse trend in both the species and were significantly different in L. rohita at higher temperatures. The decrease in the liver glycogen level of C. mrigala, however, was not significant. Plasma cortisol levels increased significantly whereas the ascorbic acid content in the brain and kidney of both the species decreased significantly with increasing temperatures. Total lipid content in the liver of both the species decreased significantly with increasing acclimation temperatures. The phospholipid concentration decreased in L. rohita with increasing acclimation temperatures, and in C. mrigala the values decreased up to 33 degrees C and increased at 36 degrees C. In C. mrigala, the cholesterol level decreased up to 33 degrees C and then increased at 36 degrees C, but the absolute value was lower in comparison to L. rohita. The cholesterol levels, however, were not significantly different in L. rohita. Triglycerides and free fatty acids concentrations decreased significantly with increasing acclimation temperatures in both the species. The present study indicates species-specific metabolic responses of L. rohita and C. mrigala to thermal acclimation.

Haemato-biochemical responses and induction of HSP70 to dietary phosphorus in Catla catla (Hamilton) fingerlings

A feeding trial of 120 days was conducted to study the effect of graded levels of dietary phosphorus on haematology, serum protein concentrations and HSP70 expression in fingerlings of the Indian major carp, Catla (Catla catla). Eight isonitrogenous and isoenergetic purified diets were formulated to contain graded levels of dietary phosphorus (dP), i.e., T(1), 0.1%; T(2), 0.3%; T(3), 0.5%; T(4), 0.7%; T(5), 0.9%; T(6), 1.1%; T(7), 1.3%; or T(8), 1.5%. Four hundred and eighty fish (average weight 4.23 +/- 0.016 g) were equally distributed into 24 tanks forming eight treatments with three replicates each. The fish were fed daily at the rate of 3.5% body weight in two instalments. At the end of feeding trial fish were sampled to study total RBC and WBC count, haemoglobin, serum lysozyme activity, serum total protein, albumin (A), globulin (G) concentration and HSP70 expression. Total RBC count, haemoglobin concentration and serum lysozyme activity did not vary significantly in response to different dietary phosphorus concentrations. Total WBC count was found to be significantly (P < 0.05) higher in T(1 )relative to all other treatments. Serum albumin and A/G ratio was found to be significantly lower in fish of T(1) and T(2) in relation to T(7) group (P < 0.05). Serum globulin and total protein levels remained unaffected by variations in dietary phosphorus. HSP70 expression was observed in T(1) group (0.1% dP) in gills and brain tissue, but not in liver and muscle tissues. No HSP70 expression was observed in fish of T(4) (0.7% dP) and T(8) (1.5% dP) treatments. These prima facie results suggest that dietary phosphorus had only minor influence on the haemato-biochemical parameters studied; however dietary phosphorus deficiency caused organ specific induction of HSP70 in catla fingerlings.

Persistent sub-lethal chlorine exposure augments temperature induced immunosuppression in Cyprinus carpio advanced fingerlings

Apart from increased temperature, thermal effluents discharged through cooling systems of nuclear power plants may often contain chlorine (used against bio-fouling), which may affect the immune status of fish. Therefore, a 28-day trial was undertaken to delineate the effect of high temperature and a persistent sub-lethal chlorine exposure on immunomodulation in Cyprinus carpio advanced fingerlings. Fish were acclimated to four different temperatures (26, 31, 33 and 36 degrees C) and maintained for 30 days in two different groups. One group was exposed to persistent chlorine (0.1mgL(-1)) and was compared with their respective temperature control groups (without chlorine exposure). Expression of heat shock proteins (hsp 70) was tested in muscle after 28 days using Western blotting. Haematological parameters (erythrocyte count, leucocyte count, haemoglobin), serum parameters (total protein, albumin, globulin, A/G ratio) and respiratory burst activity were tested to assess immuno-competence of C. carpio in response to temperature and chlorine exposure. Results indicated that hsp 70 was induced at 36 degrees C in temperature control groups but not in their respective temperatures in the presence of chlorine. Haematological parameters such as haemoglobin, erythrocyte and leucocyte counts appeared depressed in chlorine treated groups as compared to their respective temperature control groups. Serum protein and globulin were affected due to chlorine exposure at different acclimation temperatures. A decrease in NBT activity was recorded in chlorine treated groups as compared to their respective temperature control groups. Overall results indicate that increasing acclimation temperatures alters the immune status of C. carpio advanced fingerlings and persistent sub-lethal exposure to chlorine augments this temperature induced immunosuppression.