Improvement of nutritive value of grass pea (Lathyrus sativus) seed meal in the formulated diets for rohu, Labeo rohita (Hamilton) fingerlings after fermentation with a fish gut bacterium

Eight isonitrogenous (35% crude protein approximately) and isocaloric (4.0 kcalg(-1) approximately) diets were formulated incorporating raw and fermented grass pea (Lathyrus sativus) seed meal at 10%, 20%, 30% and 40% levels by weight into a fish meal based diet and fed to rohu, Labeo rohita, fingerlings for 80 days and fish performance was studied. A particular bacterial strain (Bacillus sp.) isolated from the intestine of adult common carp (Cyprinus carpio) reared in the wild having significant amylolytic, cellulolytic, lipolytic and proteolytic activities were used for fermentation of seed meal for 15 days at 37 degrees C. Fermentation of grass pea seed meal was effective in significantly reducing the crude fibre content and anti-nutritional factors, such as tannins, phytic acid and the neurotoxin, beta-ODAP and enhancing the available free amino acids and fatty acids. In terms of growth response, feed conversion ratio and protein efficiency ratio, 30% fermented grass pea seed meal incorporated diet resulted in significantly (P < 0.05) better performance of rohu fingerlings. In general, growth and feed utilization efficiencies of fish fed diets containing fermented seed meal were superior to those fed diets containing raw seed meal. The apparent protein digestibility (APD) values decreased with increasing levels of raw seed meal in the diets. The APD for raw seed meal was lower at all levels of inclusion in comparison to those for the fermented seed meals. The highest deposition of carcass protein was recorded in fish fed the diet containing 40% fermented seed meal. The results indicated that fermented grass pea seed meal can be incorporated in carp diets up to 30% level compared to 10% level of raw seed meal.     

Nutritional evaluation of fermented black gram (Phaseolus mungo) seed meal in compound diets for rohu, Labeo rohita (Hamilton), fingerlings

Six isonitrogenous (approximately 35% crude protein) and isocaloric (approximately 4.0 kcal g⁻¹) diets were formulated incorporating raw and fermented black gram, Phaseolus mungo, seed meal at 20%, 30% and 40% levels by weight into a fishmeal‐based control diet fed to rohu, Labeo rohita, fingerlings (mean weight, 1.81 ± 0.21 g) for 80 days for a study of fish performance. A particular bacterial strain (Bacillus sp.) isolated from the intestine of adult common carp (Cyprinus carpio) reared in the wild having significant amylolytic, cellulolytic, lipolytic and proteolytic activities was used for fermentation of seed meal for 15 days at 37 ± 2°C. Fermentation of P. mungo seed meal was effective in significantly reducing the crude fibre content and antinutritional factors such as tannins and phytic acid, and enhancing available free amino acids and fatty acids. In terms of growth, feed conversion ratio and protein efficiency ratio, the 30% fermented black gram seed meal incorporated diet resulted in a significantly (P < 0.05) better performance of rohu fingerlings. In general, growth and feed utilization efficiencies of diets containing fermented seed meal were superior to diets containing raw seed meal. The apparent protein digestibility (APD) values decreased with increasing levels of raw seed meal in the diets. The APD for raw seed meal was lower at all levels of inclusion in comparison to those for the fermented seed meals. The maximum deposition of protein in the carcass was recorded in fish fed the diet containing 40% fermented seed meal. The results indicate that fermented black gram seed meal can be incorporated in carp diets up to the 30% level compared to the 10% level of raw seed meal.     

Analyzing the responses of saccharin in context with melatonin receptors on the melanophores of the fish Labeo rohita (Ham.)

The hormone melatonin regulates the biological clock and assist in various other physiologies of vertebrates. Present work is intended to check the affinity of saccharin towards the melatonin receptors and the possible role of saccharin interference in the melatonin physiology. The present in vitro study is based on the working model of isolated scale melanophores in the dorso-lateral region of Labeo rohita. The pigment cells were incubated in the agonist and the antagonists within a limited time frame and subsequently their Melanophore Size Index (MSI) were calculated. The inferences were drafted through the observed signal transduction upshots in pigment translocations within the melanophores. Saccharin, in a wide dose range, has consistently induced a concentration-related aggregation similar to the aggregatory effect as shown by melatonin on the melanophores. Binding of saccharin with the receptors and eliciting its aggregatory effect is partially dependent on the release of neurotransmitters. The aggregatory effects were found to be significantly blocked by luzindole, K185, and prazosin, which are the potent melatonin receptor blockers, at the higher concentrations of saccharin. Hence, all the three subtypes of melatonin receptors viz. MT₁, MT₂, and MT₃ are participating in saccharin-mediated aggregations. Blocking by neomycin shows that Ca²⁺ ions are very crucial in dispensing the aggregatory effect of the sweetener. This research demands that an intensive and careful thorough study should be made about saccharin, specifically its effects upon melatonin physiology, before its unwarranted use as the food ingredients for human use.     

Analyzing the responses of saccharin in context with melatonin receptors on the melanophores of the fish Labeo rohita (Ham.)

The hormone melatonin regulates the biological clock and assist in various other physiologies of vertebrates. Present work is intended to check the affinity of saccharin towards the melatonin receptors and the possible role of saccharin interference in the melatonin physiology. The present in vitro study is based on the working model of isolated scale melanophores in the dorso-lateral region of Labeo rohita. The pigment cells were incubated in the agonist and the antagonists within a limited time frame and subsequently their Melanophore Size Index (MSI) were calculated. The inferences were drafted through the observed signal transduction upshots in pigment translocations within the melanophores. Saccharin, in a wide dose range, has consistently induced a concentration-related aggregation similar to the aggregatory effect as shown by melatonin on the melanophores. Binding of saccharin with the receptors and eliciting its aggregatory effect is partially dependent on the release of neurotransmitters. The aggregatory effects were found to be significantly blocked by luzindole, K185, and prazosin, which are the potent melatonin receptor blockers, at the higher concentrations of saccharin. Hence, all the three subtypes of melatonin receptors viz. MT?, MT?, and MT? are participating in saccharin-mediated aggregations. Blocking by neomycin shows that Ca2? ions are very crucial in dispensing the aggregatory effect of the sweetener. This research demands that an intensive and careful thorough study should be made about saccharin, specifically its effects upon melatonin physiology, before its unwarranted use as the food ingredients for human use.     

Prey capture success, feeding frequency and daily food intake rates in rohu, Labeo rohita (Ham.) and singhi, Heteropneustes fossilis (Bloch) larvae

Using the rotifer Brachionus calyciflorus and the cladocerans Ceriodaphnia rigaudi, Moina macrocopa and Daphnia carinata as prey (food) species, the capture success (CS), frequency of feeding and total daily food intake of rohu ( Labeo rohita ) and singhi ( Heteropneustes fossilis ) larvae were determined. The CS in both rohu and singhi was a direct function of their age as well as hunger level, but at any given age it was inversely related to prey size. The larvae fed more or less continuously, even during the night hours. Gut evacuation rates were slower in singhi than in rohu. The daily food consumption rates in rohu and singhi larvae were 13.3% and 17.7% at age 6 days, and 8.0 and 10.1% of the dry body weight at age 12 days, respectively. Although as adults rohu and singhi have distinct food niches, they did not differ significantly in the larval stages in the parameters studied. The implications of these findings for larval rearing in the aquaculture of rohu and singhi are discussed.     

Transcriptomic analyses of intestinal gene expression of juvenile Atlantic cod (Gadus morhua) fed diets with Camelina oil as replacement for fish oil

For aquaculture of marine species to continue to expand, dietary fish oil (FO) must be replaced with more sustainable vegetable oil (VO) alternatives. Most VO are rich in n-6 polyunsaturated fatty acids (PUFA) and few are rich in n-3 PUFA but Camelina oil (CO) is unique in that, besides high 18:3n-3 and n-3/n-6 PUFA ratio, it also contains substantial long-chain monoenes, commonly found in FO. Cod (initial mass ~ 1.4 g) were fed for 12 weeks diets in which FO was replaced with CO. Growth performance, feed efficiency and biometric indices were not affected but lipid levels in liver and intestine tended to increase and those of flesh, decrease, with increasing dietary CO although only significantly for intestine. Reflecting diet, tissue n-3 long-chain PUFA levels decreased whereas 18:3n-3 and 18:2n-6 increased with inclusion of dietary CO. Dietary replacement of FO by CO did not induce major metabolic changes in intestine, but affected genes with potential to alter cellular proliferation and death as well as change structural properties of intestinal muscle. Although the biological effects of these changes are unclear, given the important role of intestine in nutrient absorption and health, further attention should be given to this organ in future.     

Use of soybean flour (dehulled, solvent-extracted soybean) as a fish meal substitute in practical diets for African catfish, Clarias gariepinus (Burchell 1822): growth, feed utilization and digestibility

Growth and digestibility trials were conducted using African catfish, Clarias gariepinus (Burchell 1822): (1) to obtain apparent digestibility coefficient (ADC) values for capelin fish meal, soybean flour and corn meal; (2) to formulate diets based on ADC values of the protein feedstuffs; and (3) to evaluate the effects of replacing 25%, 50% and 75% of fish meal in control diets with soybean flour on growth, feed utilization efficiency and carcass composition. Supplemental methionine was added to the diet formulation in which soybean flour replaced 75% of the diet. Diets were formulated (400 g digestible protein kg⁻¹ and 15 kJ digestible energy g⁻¹ dry diet) and fed to catfish fingerlings (13.1 ± 0.5 g) to apparent satiation twice daily for 70 days. The protein and energy digestibilities of fish meal and soybean flour were high (>90% and >80%, respectively; P < 0.05). At 75% fish meal replacement with soybean flour (without methionine supplementation), growth and feed utilization efficiency indicators were depressed compared with other diet treatments which had a similar (P > 0.05) growth and feed utilization efficiency to those fed the control diet. The carcass compositions of catfish in all diets were similar (P > 0.05) and the liver histology of catfish fed any of the diets showed no alterations. The results obtained indicate that 50% of fish meal protein in practical catfish diets can be replaced with soybean flour and that catfish can effectively utilize supplemental methionine, thereby allowing up to 75% of the dietary fish meal protein to be replaced by soybean flour.     

Solute balance of a maize (Zea mays L.) source leaf as affected by salt treatment with special emphasis on phloem retranslocation and ion leaching

Strategies for avoiding ion accumulation in leaves of plants grown at high concentration of NaCl (100 mol m(-3)) in the rooting media, i.e. retranslocation via the phloem and leaching from the leaf surface, were quantified for fully developed leaves of maize plants cultivated hydroponically with or without salt, and with or without sprinkling (to induce leaching). Phloem sap, apoplastic fluid, xylem sap, solutes from leaf and root tissues, and the leachate were analysed for carbohydrates, amino acids, malate, and inorganic ions. In spite of a reduced growth rate Na(+) and Cl(-) concentrations in the leaf apoplast remained relatively low (about 4-5 mol m(-3)) under salt treatment. Concentrations of Na(+) and Cl(-) in the phloem sap of salt-treated maize did not exceed 12 and 32 mol m(-3), respectively, and thus remained lower than described for other species. However, phloem transport rates of these ions were higher than reported for other species. The relatively high translocation rate of ions found in maize may be due to the higher carbon translocation rate observed for C(4) plants as opposed to C(3) plants. Approximately 13-36% of the Na(+) and Cl(-) imported into the leaves through the xylem were exported by the phloem. It is concluded that phloem transport plays an important role in controlling the NaCl content of the leaf in maize. Surprisingly, leaching by artificial rain did not affect plant growth. Ion concentrations in the leachate were lower than reported for other plants but increased with NaCl treatment.     

Partial replacement of dietary fish oil with blends of vegetable oils (rapeseed, linseed and palm oils) in diets for European sea bass (Dicentrarchus labrax L.) over a long term growth study: effects on muscle and liver fatty acid composition and effectiveness of a fish oil finishing diet

Triplicate groups of European sea bass (Dicentrarchus labrax L.), of initial mass 5 g, were fed one of three practical type diets for 64 weeks. The three diets differed only in the added oil and were 100% fish oil (FO; diet A), 40% FO/60% vegetable oil blend (VO; diet B) where the VO blend was rapeseed oil, linseed oil and palm oil in the ratio 10/35/15 by weight and 40% FO/60% VO blend (diet C) where the ratio was 24/24/12 by weight. After final sample collection the remaining fish were switched to a 100% FO finishing diet for a further 20 weeks. After 64 weeks fish fed 60% VO diet B had significantly lower live mass and liver mass than fish fed diets A and C although SGR, FCR and length were not different between groups. There were no differences in any of the above parameters after either 14 or 20 weeks on the FO finishing diet. Fatty acid compositions of flesh were correlated to dietary fatty acids although there was selective retention of docosahexaenoic acid (22:6n-3; DHA) regardless of dietary input. Inclusion of dietary VO resulted in significantly reduced flesh levels of DHA and eicosapentaenoic acid (20:5n-3; EPA) while 18:1n-9, 18:2n-6 and 18:3n-3 were all significantly increased in fish fed the 60% VO diets. Fatty acid compositions of liver showed broadly similar changes, as a result of dietary fatty acid composition, as was seen in flesh. However, the response of flesh and liver to feeding a FO finishing diet was different. In flesh, DHA and EPA values were not restored after 14 or 20 weeks of feeding a FO finishing diet with the values in fish fed the two 60% VO diets being around 70% of the values seen in fish fed FO throughout. Conversely, and despite liver DHA and EPA levels being reduced to only 40% of the value seen in fish fed 100% FO after 64 weeks, the levels of liver DHA and EPA were not significantly different between treatments after feeding the FO finishing diet for 14 weeks. However, a 200 g portion of sea bass flesh, after feeding the experimental diets for 64 weeks followed by a FO diet for 14 weeks, contained 1.22 and 0.95 g of EPA + DHA for fish fed FO or 60% VO, respectively. Therefore, sea bass grown for most of the production cycle using diets containing 60% VO can still contribute a significant quantity of healthy n-3 HUFA to the human consumer.