Effect of dietary lipid levels on growth, body composition, and enzyme activities of larvae of butter catfish, Ompok bimaculatus (Actinopterygii: Siluriformes: Siluridae)

The Indian butter catfish, Ompok bimaculatus (Bloch, 1794), is a high-value catfish that has gained immense consumer preference in South-East Asia. However, information on the nutritional requirements of this species is scanty. Hence, an experiment was conducted to evaluate the effects of varying dietary lipid levels on growth, body composition, and activities of digestive and metabolic enzymes in larvae. Three isonitrogenous (40% crude protein) diets were formulated by supplementing fish and vegetable oil (1:1) at 4.5% (D1), 7% (D2), and 9.5% (D3) levels (containing crude lipid 5.7%, 8.0%, and 10.45%, respectively in diets D1–D3) to a fish meal- and oilcake-based formulated diet. Experimental diets were fed to butter catfish larvae (0.15 ± 0.01 g) in triplicate groups for a period of 42 days. Proximate compositions of the experimental diets, as well as fish carcass, were analyzed using standard procedures (AOAC 2005). Digestive and metabolic enzyme activities were analyzed at the completion of the experiment by standard methodology. Butter catfish larvae fed the diet D2 (8% crude lipid) resulted in the best performance in terms of weight gain (final weight 1.40 ± 0.07 g), net weight gain (1.31 ± 0.06 g), specific growth rate (5.50 ± 0.05% · day−1), and protein efficiency ratio (2.39 ± 0.17). The highest lipid deposition (2.90 ± 0.12%) in the carcass was also recorded in fish reared on diet D2. The final weight, net weight gain, protein efficiency ratio, and specific growth rate were significantly (P < 0.05) higher in D2 having 8% lipid. Moisture and lipid contents of the whole body were significantly (P < 0.05) higher in larvae fed diet D2. Amylase activity in fish significantly (P < 0.05) decreased with increasing dietary lipid levels. The maximum alkaline protease, pepsin, and lipase activities were noticed in the larvae fed diet D2. Progressive decrease in liver glucose-6-phosphate dehydrogenase activities and significant increase (P < 0.05) in the activities of neoglucogenic enzymes (glucose-6-phosphatase and fructose-1,6-bis phosphatase) were noticed with an increase in dietary lipid levels. Significantly lower (P < 0.05) activities of LDH, ALT, and AST were recorded in the group fed diet D2. Results of the study indicated that 8% crude lipid in the diet could assure optimum growth and survival of butter catfish larvae during early development. An appraisal on growth, body composition, and digestive as well as metabolic function in the butter catfish larvae recorded in the study might provide some important information to consider application of formulated diets for the larviculture of Ompok bimaculatus.

Effect of dietary lipid levels on growth, body composition, and enzyme activities of larvae of butter catfish, Ompok bimaculatus (Actinopterygii: Siluriformes: Siluridae)

The Indian butter catfish, Ompok bimaculatus (Bloch, 1794), is a high-value catfish that has gained immense consumer preference in South-East Asia. However, information on the nutritional requirements of this species is scanty. Hence, an experiment was conducted to evaluate the effects of varying dietary lipid levels on growth, body composition, and activities of digestive and metabolic enzymes in larvae. Three isonitrogenous (40% crude protein) diets were formulated by supplementing fish and vegetable oil (1:1) at 4.5% (D1), 7% (D2), and 9.5% (D3) levels (containing crude lipid 5.7%, 8.0%, and 10.45%, respectively in diets D1–D3) to a fish meal- and oilcake-based formulated diet. Experimental diets were fed to butter catfish larvae (0.15 ± 0.01 g) in triplicate groups for a period of 42 days. Proximate compositions of the experimental diets, as well as fish carcass, were analyzed using standard procedures (AOAC 2005). Digestive and metabolic enzyme activities were analyzed at the completion of the experiment by standard methodology. Butter catfish larvae fed the diet D2 (8% crude lipid) resulted in the best performance in terms of weight gain (final weight 1.40 ± 0.07 g), net weight gain (1.31 ± 0.06 g), specific growth rate (5.50 ± 0.05% · day−1), and protein efficiency ratio (2.39 ± 0.17). The highest lipid deposition (2.90 ± 0.12%) in the carcass was also recorded in fish reared on diet D2. The final weight, net weight gain, protein efficiency ratio, and specific growth rate were significantly (P < 0.05) higher in D2 having 8% lipid. Moisture and lipid contents of the whole body were significantly (P < 0.05) higher in larvae fed diet D2. Amylase activity in fish significantly (P < 0.05) decreased with increasing dietary lipid levels. The maximum alkaline protease, pepsin, and lipase activities were noticed in the larvae fed diet D2. Progressive decrease in liver glucose-6-phosphate dehydrogenase activities and significant increase (P < 0.05) in the activities of neoglucogenic enzymes (glucose-6-phosphatase and fructose-1,6-bis phosphatase) were noticed with an increase in dietary lipid levels. Significantly lower (P < 0.05) activities of LDH, ALT, and AST were recorded in the group fed diet D2. Results of the study indicated that 8% crude lipid in the diet could assure optimum growth and survival of butter catfish larvae during early development. An appraisal on growth, body composition, and digestive as well as metabolic function in the butter catfish larvae recorded in the study might provide some important information to consider application of formulated diets for the larviculture of Ompok bimaculatus.

Growth performances and nutrient compositions of pabda Ompokbimaculatus (Bloch, 1797) grown in recirculating and closed aquaculture systems

This study evaluated the growth performances and nutrient compositions of pabda Ompok bimaculatus (Bloch, 1797) in a recirculating aquaculture system (RAS) and a closed aquaculture system (CAS). The average daily weight gain (ADG) and specific growth rate (SGR) of pabda in RAS (ADG: 0.18 g/d; SGR: 3.40 %/d) was 3.61- and 1.41-folds higher than that of the CAS (ADG: 0.05 g/d; SGR: 2.40 %/d). Fish had significantly higher level of PUFA (Poly-unsaturated fatty acid) in CAS (41%) than in RAS (33%). The ratio between omega-3 and omega-6 fatty acids in RAS and CAS were 0.73 and 0.69, respectively. This study’s results have demonstrated that the culture of pabda in RAS is more suitable than CAS in terms of growth. J. Asiat. Soc. Bangladesh, Sci. 47(1): 1-12, June 2021

Diverse activities and biochemical properties of amylase and proteases from six freshwater fish species

This study investigated the biochemical properties, enzyme activities, isoenzyme pattern, and molecular weight of three types of digestive enzyme from six freshwater fish species: Puntius gonionotus (common silver barb), Puntioplites proctozysron (Smith’s barb), Oreochromis niloticus (Nile tilapia), Hemibagrus spilopterus (yellow mystus), Ompok bimaculatus (butter catfish), and Kryptopterus geminus (sheatfish). The optimum pHs for amylase and alkaline protease activities were 7.0–8.0 and 8.0–10.0, and the optimum temperatures were 45–60 °C and 50–55 °C, respectively. A pepsin-like enzyme was detected in all three carnivorous fishes (Ompok bimaculatus, Kryptopterus geminus, and Hemibagrus spilopterus) with optimum reaction pH of 2.0 for each and optimum reaction temperatures 50–55 °C. In optimum reaction conditions, the amylase and alkaline protease from Puntioplites proctozyron showed the highest activities. Lower activities of all enzymes were observed at temperature (29 °C) of Lam Nam Choen swamp than at the optimum reaction temperatures. The fish species contained one to three and five to eight isoforms of amylase and alkaline protease, respectively, with molecular weights from 19.5 to 175 kDa. Both the alkaline proteases and amylases were stable in wide pH and temperature ranges.

Assessment of growth and production potential of Indian butter catfish Ompok bimaculatus as a substitute for mrigal Cirrhinus mrigala in polyculture of Indian major carps

The growth and production of Indian butter catfish Ompok bimaculatus, popularly known as ‘pabda’ with Indian major carps (IMCs, catla, rohu and mrigal) was evaluated with an aim to introduce this fish into carp-based polyculture systems. Nine earthen ponds of similar dimensions were used for this study. The duration of culture was eight months and three species compositions, viz., catla, rohu and mrigal (4:3:3) (T1), with 100% replacement of mrigal with pabda (T2) and 50% replacement of mrigal with pabda (T3) were used. The overall fish stocking density was 7500 fingerlings per ha. The fish were fed with farm-made feed (21.8% CP) @ 2-4% of their body weight. Pabda attained highest growth and survival in T2 and the introduction of pabda did not affect the overall survival, growth and production of catla and rohu. It also did not affect the overall fish production in terms of quantity (p≥0.05) in all the treatments. The dietary overlapping indices between the co-habiting fishes were insignificant across the treatments except for pabda and mrigal in T3 (0.74). Thus, it is concluded that co-culture of pabda and IMCs is possible by replacing mrigal partially or fully to have a higher return in terms value from the carp-based culture system.

The morphohistology and fine anatomy of the olfactory organ in pabda catfish, Ompok bimaculatus (Bloch, 1794)

The organization of the olfactory system in Ompok bimaculatus (Siluriformes: Siluridae) were investigated by histological and ultrastructural analysis. The nasal chamber was totally engrossed by a boat shaped elongated olfactory rosette with numerous lamella. Histomicroscopically, each lamella was comprised of central core bounded on both sides by the cellular elements of olfactory epithelium. The central core was composed of thick connective tissue, nerve fibres and blood capillaries. The cellular components of the olfactory epithelium were identified based on their staining vigour, architecture, structural characteristics and surface features. The sensory epithelium contained morphologically recognizable ciliated, microvillous and rod receptor neurons. Labyrinth cells, scattered lymphatic cells, secretory mucous cells, stratified epithelial cells bearing microfolds and condensed ciliated supporting cells were observed in the indifferent epithelia. The basal cells were submerged in the deeper zone of mucosa above the basal lamina. Different sensory and nonsensory cells of the olfactory lining were associated with chemical stimulation of the fish studied. This species acquires a well developed olfactory sense for exploring the aquatic environment and able to determine the chemical changes in the surroundings.