Growth performance and feeding utilization of alternative feed for adult horseshoe crabs Carcinoscorpius rotundicauda kept in captivity

The aquafeed development has been initiated for horseshoe crabs in captivity. However, much of the attentions were to the juveniles for their widely used in research. Until recently, the research had incorporated the adult horseshoe crabs. This study aims to 1) determine the best alternative feeds for adult males of Carcinoscorpius rotundicauda, 2) measure the acceptance rate of feed, and 3) feeding utilization. Three semi‐moist pellets were either developed or purchased: fish (Decapterus russeli) and cockle (Anadara granosa) pellets (A), fish pellets (B) and keropok pellets (C). Natural feeds act as control: cockle, Anadara granosa (D) and fish, D. russeli (E). The horseshoe crabs were fed daily for 5 weeks and were analysed on their feed percentage consumption, body weight changes, feeding rate (FR), absorption efficiency (AE), feeding conversion ratio (FCR) and specific growth rate (SGR). Feed A was consumed the most (56.21%) with the highest FR (1.88%). It was influenced by the pellet's hardness, where horseshoe crabs favoured softer pellets. Body weight changes, FCR and SGR also showed a similar trend of favouring alternative feed over natural feed. Alternative feeds served a better feed than the natural feed and can be an option for future natural feed replacement for adult horseshoe crabs in captivity. Alternative feed served a better diet than the natural feed and Feed B served the best feed among the three alternative feeds with good C. rotundicauda growth performance and the feed itself is cost‐wise.     

Effects of extensive bottom cultivation of tropical oyster <Emphasis Type="Italic">Crassostrea belcheri</Emphasis> on benthic invertebrate community structure in Ban Don Bay,Suratthani Province,Southern Thailand

The diversity, distribution, and species richness of benthic invertebrates were examined under extensive bottom cultivation of the tropical oyster Crassostrea belcheri during the summer of 2015 at Ban Don Bay, Suratthani Province, Southern Thailand. Oyster farms that had been operating for 25 years were selected for the study, and four sampling sites were allocated along each transect as (i) at the center of the farm, (ii) inside the farm, (iii) at the farm boundary, and (iv) a reference site. Results indicated that a total of 23 families and 28 species of benthic invertebrate taxa were recorded from the four sampling sites, and the macrobenthic invertebrates inhabiting all study sites consisted mainly of gastropods (11 species), polychaetes (11 species), and bivalves (8 species). No significant differences in total density, diversity index, evenness index, and species richness index of benthic invertebrates were found among each sampling site (P?>?0.05). Significant differences in total nitrogen, nitrate, nitrite, total ammonia, sulfide, total phosphorus, organic matter, and grain sizes of sediment were found among each sampling site, but no significant differences in pH and total nitrogen were found. Among the independent variables analyzed, correlation analysis showed relationships between benthic diversity indices and abiotic variables. There were no clear patterns of differences in the detrimental environmental effects between sampling site locations, which indicated a minimal ecological impact of oyster cultivation.     

The effects of the tank colour on growth performance and physiological responses in fingerling grouper,Epinephelus coioides

In this study, the effects of different background colours on growth performance and physiological parameters of Epinephelus coioides were investigated. One hundred eighty E. coioides (average weight 18.16 ± 0.07 g) were distributed in black, white and blue 300‐L tanks and fed to satiation for 60 days. The tank colour had no significant effect on the weight gain, condition factor, hepatosomatic index and specific growth rate (p > .05). The lowest amount of viscerosomatic index and the highest carcass protein were recorded in the white tank (p < .05). Daily food intake, feed conversion ratio and plasma glucose were significantly higher in the blue tank (p < .05). The highest levels of haematocrit and plasma triglyceride were observed in the white tank, while the total protein and albumin were higher in the black tank compared to the other tanks. The tank colour had no significant effects on the plasma cortisol level (p > .05). Our findings showed that colours used in this study did not evoke stress and thus had no effect on growth, but some metabolic adaptation occurred in each colour to achieve optimum growth.     

Replacement of fish oil with a DHA‐rich Schizochytrium meal on growth performance,activities of digestive enzyme and fatty acid profile of Pacific white shrimp (Litopenaeus vannamei) larvae

This trial was conducted to evaluate the effects of replacing dietary fish oil with Schizochytrium meal for Pacific white shrimp (Litopenaeus vannamei) larvae (initial body weight 4.21 ± 0.10 mg). Six test microdiets were formulated using Schizochytrium meal to replace 0 g/kg, 250 g/kg, 500 g/kg, 750 g/kg, 1000 g/kg or 1500 g/kg fish oil DHA. No significant differences were observed in survival, growth, final body length and activities of digestive enzyme among shrimp fed different diets (p > .05). No significant differences were observed in C20:5n‐3 (EPA) in muscle samples (p > .05). C18:3n‐3 and C20:4n‐6 in muscle increased as Schizochytrium meal replacement level increased (p < .05). No significant differences were observed in C22:6n‐3 (DHA) and n‐3 fatty acids among shrimp fed diets that algae meal replaced 0 g/kg ‐ 1000 g/kg of fish oil. Shrimp fed diet R150 had higher DHA content than other groups and had higher n‐3 fatty acids than that of shrimp fed diets R50, R75 and R100 (p < .05). C18:2n‐6, PUFA and n‐6 fatty acids in muscle increased, while n‐3/n‐6 ratio decreased with increasing algae meal replacement level from 0 g/kg to 1000 g/kg (p < .05). In conclusion, Schizochytrium meal could replace 1500 g/kg fish oil DHA in the microdiets without negatively affecting shrimp larvae survival, growth and activities of digestive enzyme.     

Earthworm,Eisenia fetida,bedding meal as potential cheap fishmeal replacement ingredient for semi‐intensive farming of Nile Tilapia,Oreochromis niloticus

The study amalgamated earthworm and agro‐industrial wastes through vermicomposting and then evaluated the potential of the bedding (mixture of Eisenia fetida and vermicompost) to replace fishmeal in semi‐intensive farming of Oreochromis niloticus. The bedding was used to substitute fishmeal at inclusion rates of 100, 60, 30 and 0% (D100, D60, D30 and control D0). In triplicates, the four homogeneous diets were fed to quadruplicate groups of 30 g O. niloticus for 112 days. There was no significant difference (p > .05) in mortalities, average length gain and FCR among all tests. Nevertheless, diet D0 had significantly (p < .05) superior amino acid profile, low fibre content and fish carcass crude protein (63.2 ± 0.72% dry matter). Subsequently, D30 and D0 produced fish with significantly higher (p < .05) mean weight gain (256.03 ± 0.4 g) and biomass (369,136 g) respectively. On to the contrary, diet D100 had significantly higher (p < .05) crude lipids content (9.4 ± 0.6% dry matter), economic returns and profit index than the control diet due to the comparatively low cost of producing the earthworm bedding. This simple biotechnology can commercially be upscaled to sustainably produce cheap and nutritious fish feed capable of increasing yields and maximizing profits.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

Growth performance,haematology, antioxidant status,immune response and histology of common carp (Cyprinus carpio L.) fed biofloc grown on different carbon sources

A 10 weeks trial was performed to investigate how different carbon sources (sugar beet molasses: SBM+BFT, sugar: S+BFT, corn starch: CS+BFT) along with control affect welfare status of common carp (Cyprinus carpio L.) fingerlings in biofloc‐based tanks. Three hundred healthy fingerlings (22.5 ± 0.2 g) were randomly distributed in 12 tanks (70 L) at a density of 8.02 kg/m³ (25 fish/tank). The fish in BFT treatments fed only 75% feeding rate of control. At the end of the experiment no differences were seen between the groups in case of growth performance, but the fish reared in CS+BFT had a significant lower food conversion ratio compared with the others (p < .05). Different carbon sources did not affect on haematological parameters (p > .05). Total serum protein and antibody concentration differed in treatments, and the highest values were found in S+BFT and CS+BFT treatments (p < .05). No significant differences were observed in case of lysozyme, superoxide dismutase and complement activity in treatments (p > .05), whereas the fish in BFT treatments showed a significant higher total antioxidant capacity and lower glutathione peroxidase than the control (p < .05). Different carbon sources resulted in no change in goblet and kupffer cells in intestine and liver respectively. The highest relative percentage survival was obtained in the CS+BFT and S+BFT (50%) in comparison with SBM+BFT (20%) treatment. The results obtained in this experiment, suggest that corn starch improves immune response, diseases resistance and histology of digestive and respiratory systems in carp fingerlings when used as a carbon source in zero water exchange system.     

Effects of partial replacement of fishmeal with blood meal and dried porcine soluble on the growth,body composition and intestinal morphology of Cyprinus carpio

A 12‐week feeding trial was conducted to assess the impact of fishmeal replacement with blood meal or dried porcine solubles on the growth performance, body composition and intestinal morphology of common carp (Cyprinus carpio). Fishmeal was 50% substituted with either blood meal or dried porcine solubles, or two‐third substituted with both alternative products, at a 1:1 ratio. There was no significant difference in survival, final weight, weight gain ratio, feed conversion ratio or condition factor between the control and experimental groups (p > .05), although the visceral somatic index of the blood meal group was higher than that of the control group (p < .05). Crude lipid content was significantly higher in the dried porcine soluble group than that in the control group (p < .05), while other nutrient levels were not significantly different (p > .05). The amino acid composition of each experimental group was not significantly different from that of the control (p > .05). The intestinal villus height and fold depth of each experimental group were significantly lower than those of the control group (p < .05). The results of this study show that two‐third fishmeal substituted with both blood meal and dried porcine solubles, at a 1:1 ratio, is the optimal fishmeal replacement for common carp growth.     

Effect of dietary soybean lecithin on growth parameters,digestive enzyme activity,antioxidative status and mucosal immune responses of common carp (Cyprinus carpio)

Common carp, Cyprinus carpio (13.54 ± 0.48 g), were fed soybean lecithin‐incorporated diets for 8 weeks. After the feeding trials, the different groups of fishes were assessed by survival, growth parameters, digestive enzymes, antioxidant enzyme activities, mucosal immune parameters, etc. The lecithin‐incorporated diets (10–30 g kg^–1) helped to increase the weight gain significantly (p < .05) compared with control groups; activity of digestive enzymes was also significantly (p < .05) higher compared with experimental groups. The antioxidant enzymes including catalase and serum superoxide dismutase were significantly (p < .05) higher in the C. carpio fed lecithin‐incorporated feed than the ones fed the control feed. The serum thiobarbituric acid‐reactive substances and serum glutathione peroxidase activity did not differ significantly (p > .05) between control and experimental groups. The positive correlation supported that antibacterial activity was significantly (p < .05) increased with increasing concentration of lecithin in the diets. Among the different mucosal immune parameters, lysozyme, protease and esterase activities were significantly (p < .05) increased with lecithin‐incorporated diets. The results of this study confirm that 20 and 30 g kg^–1 lecithin inclusion in diets helped to enhance the activities of digestive enzymes, antioxidant enzymes, antibacterial factors and mucosal immune parameters in C. carpio.