Ameliorating effects of dietary mixture of Withania somnifera root extract and vitamin C in Labeo rohita against low pH and waterborne iron stresses.

The present study was conducted to elucidate the possible effect of a combination of Withania somnifera (Ashwagandha) root extract and dietary l-ascorbic acid (vitamin C) on the immune responses and survivability in Labeo rohita fingerlings against low pH and waterborne iron toxicity. Four diets were prepared containing 0% (control), 0.01% (T1), 0.1% (T2) and 1.0% (T3) of a combination of Withania somnifera (Ashwagandha) root extract and dietary l-ascorbic acid (vitamin C) at the rate of 1:1 (w/w). Fishes were fed for 60 days to find out the best dose and duration of feeding by examining different haematological (haemoglobin, haematocrit, total RBC count, total WBC count, MCV, MCH and MCHC), immunological (NBT, lysozyme and total immunoglobulin activity) and biochemical (glucose, total protein, ALP, SGPT and SGOT level) parameters on 7, 15, 30 and 60 days of feeding. The best response was observed in fish fed with diet T3 within 15 days. The result showed a significant (p < 0.05) increase in haemoglobin, haematocrit, total RBC count, total WBC count, NBT, lysozyme activity, total immunoglobulin and total protein whereas a significant (p < 0.05) decrease in glucose, ALP, SGPT and SGOT level compared to control. Challenged study against waterborne iron (6.02 mg l-1) and low pH (4.2-4.5) after feeding the fish for 15 days with diet T3 showed significantly (P < 0.05) higher protection than control. The study concludes that inclusion of 1.0% Withania somnifera (Ashwagandha) root extract and dietary l-ascorbic acid (vitamin C) combination in diet have a stimulatory effect on immune response and reduces the effect of multiple stresses (i.e., low pH and waterborne iron toxicity) in L. rohita fingerlings.

Effect of miconazole nitrate on immunological response and its preventive efficacy in Labeo rohita fingerlings against oomycetes Saprolegnia parasitica.

This study evaluated the effect of sublethal doses of antifungal drug miconazole nitrate (MCZ) on immunological responses and its role as a prophylactic drug against S. parasitica in Labeo rohita fingerlings. Fish were fed with sublethal doses of MCZ, that is, T1-6.30 mgMCZ kgBW-1 , T2-12.61 mgMCZ kgBW-1 and T3-25.22 mgMCZ kgBW-1 , and sampling was done at different time intervals for 240 hr. Immunological parameters viz. lysozyme activity, oxygen radical production and plasma antiprotease activity showed significant enhancement (p < 0.05) in fish fed with T2 and T3 doses. Expression of immune-relevant genes such as TLR-22 and ß2-M showed significantly higher expression at 6 hr and 24 hr of sampling in both liver and head kidney. However, these genes showed a downregulation after 120 hr of sampling in both the tissues. Preventive efficacy study showed that single dose of MCZ provides protection against oomycetes up to the fourth day of infection. Significantly higher mortality was observed in control diet-fed fish as compared to fish fed with MCZ medicated diet. Thus, it can be concluded that the MCZ can act as a potent antifungal agent for preventing oomycetes infection as well as to enhance the immune response.

Muli bamboo (Melocanna baccifera) leaves ethanolic extract a non-toxic phyto-prophylactic against low pH stress and saprolegniasis in Labeo rohita fingerlings.

Bamboo (Melocanna baccifera) plant plays a significant role in traditional Asian medicine and it can be used as an alternative to various chemo-therapeutics or prophylactic agents used in aquaculture. In the present study, the 1st experiment was done for the preparation of extracts from bamboo leaves by using 90% alcohol as a solvent. In the 2nd experiment, toxicity study was carried on Labeo rohita fingerlings (average length of 10.3 ± 1.5 cm and weight 18.5 ± 1.5 g) using BLAL (Bamboo Leaf Alcoholic) extract and it did not show any mortalities in fish even at the dose of 20 g kg-1 body weight, which can be regarded as virtually non-toxic with minimal effect. The 3rd experiment was conducted to find out the effect of BLAL extract based isocaloric and isonitrogenous feed (doses: control- 0.0%, diet T1-0.01%, diet T2-0.1%, diet T3-1% BLAL extract kg-1 feed) on the haemato-immuno-biochemical parameters of L. rohita fingerlings (average length 15.7 ± 1.5 cm and weight 20.2 ± 1.5 g). Regular sampling was done (on 7th, 15th, 30th and 60th day of feeding) for different haematological, immunological and biochemical parameters. The study revealed that the best response occurred within 7 days of feeding with BLAL extract and long-term feeding have shown immunosuppressive condition in the fish. In the 4th experiment, fish were exposed to multiple stressors like low pH stress, and Saprolegnia parastica infection after feeding with BLAL extract (0.1%) based feed for 7 days. The study showed that the BLAL extract can make fish resistant to single stress however, not able to reduce the fish mortality under multiple stresses (S. parastica infection under low pH). Thus, it can be concluded that the BLAL has the potentiality to be used as a non-toxic phyto-prophylactic which can induce non-specific immune response, reduces the low pH stress responses and increases the resistance against saprolegniasis under neutral pH condition in rohu fingerlings.

Feeding pyridoxine prevents Saprolegnia parasitica infection in fish Labeo rohita.

A 60-day experiment was carried out to delineate the role of dietary pyridoxine (DP) in Labeo rohita fingerlings in modulating immunity and prevention of fungal infection. Two hundred and seventy fingerlings were randomly distributed into three treatments in triplicates. Three iso-caloric and iso-nitrogenous purified diets were prepared with graded levels of pyridoxine. Three experimental groups were C (0.0% DP), T1 (0.01% DP) and T2 (0.02% DP). The role of dietary pyridoxine in modulating immunity and prevention of fungal infection was assessed by haemato-immunological parameters like erythrocyte counts (EC), leucocyte counts (LC), haemoglobulin (Hb), packed cell volume (PCV), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), nitro-blue tetrazolium (NBT), phagocytic activity, albumin, globulin, total plasma protein, albumin/globulin and by challenge study with Saprolegnia parasitica, where relative percentage survival (RPS) were recorded. Hb, PCV, MCV, MCH, NBT, total plasma protein, albumin, globulin contents, lysozyme and phagocytic activity was significantly (P < 0.05) higher in DP fed group. Significantly (P < 0.05) higher RPS was recorded from T2 group fed with 0.02% DP for 45 days. Hence, DP has the capacity to stimulate nonspecific immunity and increase resistance to S. parasitica infection in L. rohita fingerlings.