Although nucleotides (NT) have long been implicated as feed attractants in both vertebrate and invertebrate species, research into potential growth and health benefits of dietary NT in aquaculture species has just been implemented in early 2000s. To date, research pertaining to NT supplementation in aquafeed as functional nutrients has shown rather consistent and encouraging, beneficial results in fish and shrimp health management. Dietary NT serve a marked role to enhance growth in early stages of development, improve reproductive performances of brood fish, enhance larval quality, increase stress and disease resistance, modulate immune functions and improve intestinal morphology and gut microbiota of fish and shrimp. NT have also been used as functional supplement in alternative protein based diet, where NT was found as an effective supplement to increase the efficiency of utilizing alternative proteins. However, still there are numerous gaps in existing knowledge about exogenous NT administration to fish and shrimp including various aspects of digestion, absorption, metabolism, administration duration and age/size‐related responses. Adoption of different molecular technologies, like proteome modification and study of several gene expression pattern related to growth, immunity, gut health and stress resistance in details are important for exploring the underlying mechanisms of NT functions in improved growth and health performances of fish and shrimp. Efforts are also needed on production technologies to reduce the NT cost. Moreover, extensive research information is also required regarding the use of NT in alternative protein and lipid based diet to develop cost‐effective, ecofriendly functional aquafeed in near future.

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The nutritional value of spirulina in aquafeeds has been studied extensively as a fishmeal replacer or as a functional feed additive to increase growth and health performance of fish in the last decade. Despite increased interest in spirulina research in aquaculture, its increased production cost still limits its use in commercial rations. Zarrouk’s medium is the standard substrate used for growing spirulina. Although this medium offers optimal biomass production, it incurs higher costs due to the expensive components needed for concocting the medium. In this regard, development of cost‐effective alternative culture medium or techniques is necessary for the industrial‐scale production of these microalgae. This paper reviews research on different alternative media for spirulina cultivation and its nutritive value as an aquafeed. Numerous alterations in the composition of Zarrouk’s medium with cheaper chemical ingredients have been explored as a potential substitute for cost‐effective microalgae cultivation. Industrial and processing wastes and by‐products with appropriate nutrient profiles for growing spirulina are also being considered as alternative culture media. The use of rice bran or other cheaper agricultural by‐products, as a cost‐effective growth medium for commercial‐scale spirulina production has yet to be explored extensively in agriculture‐based countries, especially in rice‐producing Asian countries.

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Alternative sources of fish oil (FO) are one of the major problems in aquaculture; therefore, the goal of the present study was to examine insect (black soldier fly larvae) oil (BSLO) as a potential replacer of fish/soy oil in juvenile rainbow trout (initial average weight of 32 ± 0.15 g) feed. Four diets were formulated wherein FO (control diet) was completely replaced with either soybean oil (SO) or BSLO, and an additional BSLO-based diet supplemented with 1.5% bile acid (BSLO + BA) were fed to the fish for 10 weeks. Growth performance of the BSLO fed group was similar ( P > 0.05) to that of the FO and SO fed groups, however, the fish fed BSLO + BA diet registered the lowest growth ( P < 0.05). Oil sources did not ( P > 0.05) affect the major nutrient content of whole-body, however, the fatty acid composition of the muscle and liver was influenced ( P < 0.05), with the highest 14:0, 16:0, and total saturated fatty acid detected in BSLO or BSLO + BA fed trout compared to the others ( P < 0.001). No significant differences were observed in eicosapentaenoic acid + docosahexaenoic acid (EPA + DHA) or total n-3 polyunsaturated fatty acid (PUFA) content in muscle among the groups, whereas, the highest EPA:DHA and n-3:n-6 ratios were detected in the FO group. Gene expression for fatty acid binding protein ( fabp ) , fatty acid synthase ( fas ), and Δ5 desaturase in the liver was lower in FO ( P < 0.05), while BSLO + BA registered the highest Δ6 expression ( P = 0.006). Supplementation of BA in the BSLO diet increased superoxide dismutase (SOD) and catalase (CAT) activities compared to the other groups ( P < 0.05). In conclusion, BSLO could serve as a substitute for FO and SO in rainbow trout diet without negatively impacting growth performance, whole-body composition and nutrient retention, and modulate the expression of fatty acid metabolism-related genes in rainbow trout.

A 56‐day feeding trial was done to investigate the interactive effects of astaxanthin (Ax) and vitamin E (α‐Toc) on the performance of kuruma shrimp (Marsupenaeus japonicus). A 2 × 3 factorial experiment was conducted with six experimental diets containing two levels of Ax (0 and 0.6 g/kg diet [Ax0 and Ax0.6]) and three levels of α‐Toc (0, 0.2 and 1 g/kg diet [α‐Toc0, α‐Toc0.2 and α‐Toc1]). The results indicated that growth performance was significantly (p < 0.05) increased in shrimp fed with the Ax0.6 × α‐Toc0.2 diet. Interactive effects between Ax and α‐Toc on the growth parameters were observed. Furthermore, pigmentation performance was significantly (p < 0.05) better in the Ax0.6 groups. Interaction between Ax and α‐Toc was also found in the Ax content of shrimp body parts. Interestingly, dietary α‐Toc helped to reduce the Ax consumption rate, promote the absorption and increase the deposition of Ax in the muscle. Shrimps from the Ax0.6 groups showed significantly (p < 0.05) improved hepatopancreatic digestive enzyme activities compared with those of the Ax0 groups. Although no interactive (p > 0.05) effects were found between dietary α‐Toc and Ax on total haemocyte count and tolerance against freshwater, dietary Ax and α‐Toc supplementation showed better performance on these two parameters. It was concluded that dietary Ax and α‐Toc functioned synergistically, and the shrimp fed with the diet containing 0.6 g Ax/kg diet Ax and 0.2 g α‐Toc/kg diet showed improved growth and pigmentation performance compared with the other groups in the current study.

Purpose The purpose of this paper is to conduct consumer profile analysis for chicken, beef, mutton, fish and egg to better adapt the marketing mix for each type of food in Bangladesh. Design/methodology/approach This paper investigates the mean consumption frequency of chicken, beef, mutton, fish and egg, following 658 questionnaire survey results. The sociodemographic variables used in this study were: sex, age, gender, educational level, social class, number of family members in the home, the presence of minors less than 18 years in the home and geographical area. Frequency distribution, factor and cluster analysis were performed to understand the food consumption frequency and food-related lifestyle segment, respectively. The statistical significance for differences among the mean values of different foods was tested by Snedecor’s F-test. Findings Egg was the most frequently consumed; 77 per cent of respondents ate egg once daily. Chicken was the second most consumed (62 per cent), whereas fish was third (59 per cent). Mutton was in the fourth place of consumption frequency level. However, 24 per cent of respondents did not consume mutton. The same types of behaviour were observed for beef, which was the least consumed (7 per cent) once daily, 48 per cent once a week, whereas 13 per cent did not consume it. There was no specific consumer behaviour pattern for the sociodemographic variables and types of food studied here. Originality/value This research provides the status of consumer preferences towards chicken, beef, mutton, fish and egg consumption in Bangladesh.

Colistin (polymyxin E) is widely used in animal and human medicine and is increasingly used as one of the last-resort antibiotics against Gram-negative bacilli. Due to the increased use of colistin in treating infections caused by multidrug-resistant Gram-negative bacteria, resistance to this antibiotic ought to be monitored. The study was undertaken to elucidate the molecular mechanisms, genetic relationships and phenotype correlations of colistin-resistant isolates. Here, we report the detection of the mcr-1 gene in chicken-associated Salmonella isolates in Bangladesh and its in-silico functional analysis. Out of 100 samples, 82 Salmonella spp. were isolated from chicken specimens (liver, intestine). Phenotypic disc diffusion and minimum inhibitory concentration (MIC) assay using different antimicrobial agents were performed. Salmonella isolates were characterized using PCR methods targeting genus-specific invA and mcr-1 genes with validation for the functional analysis. The majority of the tested Salmonella isolates were found resistant to colistin (92.68%), ciprofloxacin (73.17%), tigecycline (62.20%) and trimethoprim/sulfamethoxazole (60.98%). When screened using PCR, five out of ten Salmonella isolates were found to carry the mcr-1 gene. One isolate was confirmed for Salmonella enterica subsp. enterica serovar Enteritidis, and other four isolates were confirmed for Salmonella enterica subsp. enterica serovar Typhimurium. Sequencing and phylogenetic analysis revealed a divergent evolutionary relationship between the catalytic domain of Neisseria meningitidis lipooligosaccharide phosphoethanolamine transferase A (LptA) and MCR proteins, rendering them resistant to colistin. Three-dimensional homology structural analysis of MCR-1 proteins and molecular docking interactions suggested that MCR-1 and LptA share a similar substrate binding cavity, which could be validated for the functional analysis. The comprehensive molecular and in-silico analyses of the colistin resistance mcr-1 gene of Salmonella spp. of chicken origin in the present study highlight the importance of continued monitoring and surveillance for antimicrobial resistance among pathogens in food chain animals.