Identifying novel plant‐based protein ingredients, including coproducts of bioengineered oilseeds, is important for sustainable trout farming. In the current study, effects of a bioengineered oilseed ingredient, a high docosahexaenoic acid (DHA) canola (NS‐B50027‐4) meal, have been evaluated in relation to conventional canola meal in rainbow trout diets. For this purpose, three experimental feeds for rainbow trout were produced by adding 20% of the DHA canola meal and control canola meals with other basal ingredients for the first two diet groups, diet‐1 and diet‐2, respectively, and a mixture of 10% DHA canola and 10% control canola meals were added with similar basal ingredients for producing the third experimental diet (diet‐3). Diets were fed to ~42 g sized rainbow trout at the start for a period of 64 days. Following the feeding trial, the growth performance indices (final weight, percentage weight gain, and specific growth rate) were not significantly different among treatments. However, feed intake of fish fed diet‐3 was significantly lower ( p < 0.05) than that of fish fed the other treatments. Diet‐3 fed fish also had higher lipid retention when compared to diet‐2, with diet‐1 having an intermediate value. Among the measured blood biochemical parameters, only the alanine amino transferase (alanine transaminase [ALT]) value was significantly influenced, with fish fed diet‐1 having a significantly lower ( p < 0.05) value compared to other treatments, suggesting a modulation of hepatic metabolism. Whole‐body proximate composition was not significantly influenced by dietary treatments. Whole‐body α‐linolenic acid content was significantly lower ( p < 0.05) in fish fed the conventional canola meal diet (diet‐2), reflecting the lower α‐linolenic acid content of that diet. Although DHA canola meal contains relatively higher DHA, whole‐body DHA content of fish fed the DHA canola meal was not significantly influenced, likely because the meal has a low residual lipid content and fish oil (FO) supplied more than 97% of dietary DHA in all diets. In summary, no significant differences in growth or feed conversion were detected between fish fed 20% DHA canola meal and those fed 20% conventional canola meal. While fish fed diet‐1 had lower plasma ALT, liver histopathology should be evaluated in a future study to better characterize the impact on liver health. This study supports the incorporation of the DHA canola meal, a coproduct of high DHA omega‐3 canola (NS‐B50027‐4) oil production, into rainbow trout diets as a nutritional ingredient.
Cumulative welfare is defined as the balance of all experiences shaping an animal’s quality of life over its lifespan. For cultured fish, optimizing cumulative welfare requires identifying the factors that modulate biological processes linked to negative and positive experiences. This study investigated whether behavioral thermoregulation represents one such factor in Atlantic salmon ( Salmo salar ) during the freshwater phase. The fish were reared for 5 months in thermally enriched (allowing thermoregulation) or constant‐temperature (non‐thermoregulatory) environments, and their thermal behaviors were documented. Welfare was assessed through mortality, growth, and parameters linked to oxidative damage in brain and muscle tissues. These parameters included free radicals, superoxide dismutase 1 ( sod1 ), glutathione peroxidase 1a ( gpx1a ), 8‐hydroxy‐2 ′ ‐deoxyguanosine (8‐OHdG), telomere‐to‐single‐copy gene ( T / S ) ratio, and 5‐methylcytosine (5‐mC). The ability to behaviorally thermoregulate was associated with lower mortality, greater growth, and elevated antioxidant enzyme expression compared to the non‐thermoregulatory group. Thermoregulatory fish also showed lower 8‐OHdG levels in both tissues, a stable brain T / S ratio over time, and 5‐mC changes indicative of brain hypomethylation and muscle hypermethylation. Despite these complex time, tissue, and group‐dependent patterns, the principal component analysis (PCA)‐derived index revealed consistently higher welfare scores for the thermoregulatory group. Among all indicators evaluated, PCA‐based coefficient values identified 8‐OHdG and mortality as the variables with the largest contribution to the cumulative welfare index. These findings provide experimental evidence of a link between behavioral thermoregulation and the modulation of biological processes related to an optimized cumulative welfare state. This study contributes to the integration of retrospective and prospective dimensions into animal welfare management in aquaculture.
This study comprehensively analyzed the effects of different cultivation methods (CMs) and densities on the growth of Gracilariopsis lemaneiformis in indoor settings and two representative sea areas, Ailun Bay and Nanri Island, located in the northern and southern parts of China. The findings indicate that horizontal hanging cultivation significantly enhanced macroalgal growth and biomass production in both sites. In contrast, vertical hanging cultivation resulted in significantly lower yields, primarily due to inadequate illumination below certain water depths and epibiont infestation. Moreover, integrated multitrophic aquaculture (IMTA) systems co‐cultivated with scallops demonstrated biomass and specific growth rates (SGR) similar to those of horizontal hanging cultivation, and nutrient concentrations in the IMTA areas were lower than those in the scallop monoculture areas. These observations suggest a potential role for G. lemaneiformis in nutrient mitigation. Regarding cultivation density (CD), lower densities were beneficial for higher SGR in both regions, with limited impact on final biomass, suggesting that moderately reducing CD could promote growth and reduce seedling use. Within optimal ranges, light intensity positively correlated with SGR; however, excessive light appeared to induce light‐related stress or photoacclimation, as well as pigment reduction, in horizontal hanging cultivation, suggesting adverse effects under high‐light conditions. In vertical hanging cultivation, reduced light increased pigment content, likely as an adaptive response to insufficient light, while increased density led to decreased SGR indoors, suggesting that resource competition under high‐density conditions may limit SGR. Our research indicates that horizontal hanging cultivation at a lower density (0.15 kg/m) can enhance SGR and reduce seedling use without compromising final biomass, suggesting a potential strategy for improving cultivation efficiency. However, the practical adoption of this strategy should also consider site‐specific factors such as seed costs, labor availability, and seasonal risks. This study provides useful information for optimizing seaweed cultivation practices and highlights the importance of adopting ecological and sustainable methods in aquaculture.
Variations in aquatic environmental characteristics and food resource availability across different habitats lead to habitat‐specific differentiation in the structure and function of the fish digestive system. As a key functional component in maintaining host health, fish gut microbiota is critically important for the healthy and sustainable development of aquaculture. In this study, we investigated the gut microbiota of Glyptosternon maculatum from wild, domesticated, and farmed groups, as well as the microbiota in their habitat water, using 16S rRNA gene sequencing. Alpha diversity analysis (one‐way analysis of variance (ANOVA) with Tukey’s HSD post hoc test for multiple comparisons) revealed that the Shannon and Simpson indices of the gut microbiota were significantly higher in the wild group than in the domesticated and farmed groups ( p < 0.05), indicating greater community diversity in the wild population. Beta diversity analysis (Adonis test based on Bray‐Curtis distances) demonstrated significant separation between the wild group and the other two groups in both intestinal ( R 2 = 0.132, p = 0.026) and water ( R 2 = 0.645, p = 0.002) microbiota, while the domesticated and farmed groups showed similar microbial community structures in both gut and water samples. Mantel tests revealed that pH and dissolved oxygen (DO) were significantly correlated with gut microbial community composition, suggesting these environmental factors may influence the intestinal microbiota of G. maculatum . Functional prediction analysis (PICRUSt2) revealed habitat‐associated differences in metabolic functions of the gut microbiota, particularly in amino acid and carbohydrate metabolism pathways. In summary, these findings provide baseline data for understanding habitat‐related microbial community shifts in G. maculatum and may inform future conservation and management strategies for this species.
