The aim of this study was to determine the impact of replacing fishmeal with silkworm pupae (Bombyx mori) meal in the diet of rainbow shark Epalzeorhynchos frenatum (Fowler, 1934), on growth and maturation. Four isonitrogenous and isocalorific experimental diets (35% CP) were prepared using silkworm pupae (SWP) replacing fish meal at three different levels viz., 30% (T1), 40% (T2) and 50% (T3) and diet with only fish meal served as control (C). The experimental trail was conducted in hapas, in duplicates, installed in an earthen pond. The fish (average weight - 1.4 g and total length - 5.24 cm) were stocked @10 nos. per hapa. During the experimental period, water quality parameters were monitored routinely. The experimental diets T1, T2 and T3 performed significantly better than diet C (control) in terms of growth performance. Among the four diets, T1 showed significantly higher weight gain (5.18±0.28 g), specific growth rate, SGR (2.54±0.07% day-1), protein efficienvy ratio, PER (1.50±0.04) and food conversion ratio, FCR (1.91±0.06) compared to other treatment groups. Among all the diets, highest gonadosomatic index, GSI (14.90%) was obtained in fish fed diet T1. At the end of the experiment, all the experimental diets fed fishes showed similar stages of maturity, late vitellogenic stage. Overall, the results of the present study conclude that SWP can be used as a low-cost animal protein to replace fish meal upto 30% in the diet.
Background: Nursery rearing of Penaeus vannamei became inevitable in the Indian shrimp farming industry, since intensification of culture practices in grow-out systems caused nitrogenous wastes accumulation, diseases, mortality and premature harvests resulted in high food conversion ratio, lower production and profits. The nursery rearing in traditional water exchange systems often getting failure because of nitrogenous waste accumulation. Hence, the present experiment was planned to rear P. vannamei in bioflocs systems (BFS) with different salinities and carbon sources. Methods: The experiment was conducted in 0.22 m3 tanks with three different salinity groups viz., 35 ppt, 20 ppt and 5 ppt and in each salinity sugar, molasses used as carbon sources to maintain an estimated C/N ratio of 15:1 and controls without carbon sources. Experimental tanks were stocked @6 post larvae/l, with pre-salinity acclimatized P.vannamei seeds having 0.0029±0.0003g size and nursed for a period of 5 weeks. Result: The nitrogenous waste accumulation was reduced significantly (p less than 0.05), also average body weight and survival rate of the seeds showed significant difference (p less than 0.001) between treatments and controls and within treatments (p less than 0.05). Salinity, carbon sources and their interaction influenced the growth characteristics significantly (p less than 0.01). The present experiment manifested promising results of bioflocs nurseries in rearing of P. vannamei seeds at different salinities.
In the biofloc systems the continuous application of carbon sources led to the assimilation of nitrogenous nutrients and formation of heterotrophic bacterial biomass. The present experiment was conducted in 0.22m 3 capacity tanks in the triplicate to find out the structure, proximate composition, nutrient dynamics and growth characteristics of Penaeus vannamei in indoor biofloc systems with three different salinities (35, 20 and 5ppt) and carbon sources (molasses, sugar and rice flour) with an estimated C:N ratio of 15:1. pre salinity acclimatized P. vannamei , specific pathogen free seeds (0.2±0.04g) were stocked @100 numbers per m 3 and fed 4 times a day based on the % of body weight (from 22% to 2.5%) and reared for 10 weeks. The results revealed that the carbon application at different salinities significantly influenced the biofloc structure (Scanning Electron Microscopic images of biofloc 4000x) showed round and rod-shaped structures. Proximate composition: crude protein (p<0.001), ether extract (p<0.001) and crude fibre (p<0.05) showed significant difference between treatments. Similarly, elemental carbon composition (p<0.01), nitrogenous waste assimilation of TAN (p<0.01), nitrite (p<0.05), and nitrate (p<0.05) showed significant differences in the treatments vs. the control group. The variables also influenced the microbiota abundance {the metagenomics analysis of biofloc showed Bray-Curtis overall average dissimilarity index of 81%, and it varied from 49% to 100% between treatments & controls} and growth characteristics {average body weight (p<0.001) and survival rate (p<0.01) between treatments and controls} of P. vannamei indoor biofloc systems. Hence, the application of carbon sources at different salinities influenced the biofloc structure, proximate, elemental carbon composition, biofloc microbiota abundance, enhanced the nitrogenous waste assimilation and growth performance of P. vannamei in indoor biofloc systems.
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