This study evaluated whether partial dehydration methods alter the chemical composition of high-moisture forages. Two experiments were conducted. In Experiment 1, 20 maize silage samples were subjected to freeze-drying, forced-air oven drying, forced-air oven drying preceded by a microwave preheating step, or microwave drying. In Experiment 2, 28 forages (silages, fresh grasses, and fresh legumes) were evaluated using freeze-drying, forced-air oven drying, microwave drying, or air-fryer drying. Method effects were assessed based on water removal efficiency, nitrogenous and fibrous compound profiles, in vitro digestibility, indigestible fibre, and colorimetric properties. Microwave and air-fryer drying removed less water than freeze-drying and resulted in greater differences in nitrogenous compound concentrations and profiles, including apparent N volatilisation and greater concentrations of detergent-insoluble nitrogen. Heat application inconsistently affected fibrous components but consistently reduced in vitro dry matter digestibility without altering in vitro fibre digestibility, likely reflecting starch retrogradation and production of heat-derived artefacts soluble in neutral detergent. These modifications were most pronounced in fresh forages, indicating an interaction with their chemical matrix. Among heat-based methods, forced-air oven drying produced the least chemical alteration. Overall, heat application during partial dehydration modifies the chemical characteristics of high-moisture forages, and when freeze-drying is not feasible, forced-air oven drying best preserves the original sample composition.
Soybean oil is widely used in ruminant nutrition due to its high energy density and elevated unsaturated fatty acid content; however, its susceptibility to ruminal biohydrogenation and oxidation limits its nutritional efficiency, driving the development of technological strategies to protect lipids. In this context, condensed tannins (CT) have emerged as promising functional components for application in microencapsulated systems. This study evaluated the use of CT as a co-wall material, in combination with gum arabic, whey protein isolate, and soy protein isolate for the spray-drying microencapsulation of soybean oil, with a focus on microstructure modulation and lipid core protection. The microparticles were characterized for microencapsulation efficiency, oxidative stability, antioxidant activity, and morphology. The formulations exhibited high microencapsulation efficiency (84.89–96.67%) and low peroxide values (0.71–1.73meqO₂/kg), reflecting primary lipid oxidation (hydroperoxides), indicating effective oxidative protection of the oil. Antioxidant activity showed no linear relationship with total phenolic content, suggesting that reactivity is influenced by interactions between CT, proteins, and polysaccharides, which may affect the release of phenolic compounds from the encapsulating matrix. Scanning electron microscopy micrographs revealed predominantly spherical particles and morphological differences consistent with those of the wall composition, supporting CT’s role as a matrix structuring agent. Overall, the results demonstrate that CT incorporation modulates the microstructure and system performance, reinforcing its potential as a co-wall material in lipid microencapsulation systems for ruminant nutrition applications.
Plant essential oils are known to possess growth-promoting, antimicrobial, anti-inflammatory, and immune-enhancing properties. Thus, the effects of essential oils as dietary supplements were investigated over a 56-day feeding period to ascertain any effects on the growth performance, immune response, and intestinal microbiota composition in Japanese flounder (Paralichthys olivaceus). For the experiments, 240 Japanese flounders (yearling fish, 436.35±110.13g) in four experimental groups were supplemented with varying concentrations of plant essential oils: NC (0mg/kg, negative control), EO100 (100mg/kg), EO200 (200mg/kg), and EO400 (400mg/kg). The results indicated the 200mg/kg and 400mg/kg treatment groups exhibited significantly higher weight gain rates (80.52% and 78.62%, respectively; P = 0.040) and specific growth rates (1.04%/d and 1.03%/d, respectively; P = 0.010) than the other groups, along with a significant increase in white blood cell count (36.71 × 10^9/L and 49.45 × 10^9/L, respectively; P < 0.001) and enhanced activities of lysozyme (4.27μg/ml and 4.48μg/ml, respectively; P = 0.016), and superoxide dismutase (6.61 U/ml and 5.61 U/ml, respectively; P = 0.001). The 200mg/kg treatment group was also observed to have increased the number of goblet cells in the intestinal villi and have reduced the vacuolation rate in liver cells. Transcriptomic analysis showed differentially expressed genes significantly enriched in metabolic pathways, and cyp7a1 and plrp1 gene expression was upregulated. Additionally, metagenomic analysis revealed increased abundance of Duncaniella (0.67-3.10% and 0.698-3.07%, respectively), Bacteroides (0.79-2.37% and 0.63-2.40%, respectively), and Muribaculum (0.50-1.61% and 0.43-1.61%, respectively) in the intestinal microbiota of the 200mg/kg and 400mg/kg groups. In conclusion, composite plant essential oils exhibit significant potential as functional feed additives.
Largemouth bass (Micropterus salmoides) is one of the most economically important freshwater aquaculture species worldwide. However, the rapid expansion of its farming industry has intensified challenges related to feed resource dependence, environmental sustainability, and health management. Conventional feeding strategies relying heavily on fishmeal and antibiotics are increasingly constrained by resource limitations and ecological concerns, highlighting the need for sustainable nutritional solutions. Functional feed additives have therefore emerged as promising tools for improving production efficiency and maintaining fish health in modern aquaculture systems. This review synthesizes recent advances in the application of functional feed additives in largemouth bass aquaculture, with emphasis on studies published over the past five years. Major additive categories, including probiotics, prebiotics, phytogenic extracts, enzyme preparations, antioxidants, and immunostimulants, are systematically discussed. Their regulatory roles in growth performance, gut microbiota modulation, intestinal barrier integrity, immune responses, metabolic homeostasis, and nutrient emission control are summarized to elucidate their mechanisms of action within sustainable aquaculture frameworks. Current evidence indicates that functional additives can enhance feed efficiency, physiological resilience, and environmental sustainability by improving digestive capacity, stabilizing intestinal microecology, and regulating redox–immune balance. However, their efficacy remains highly context-dependent, influenced by additive type, dosage, and dietary help reducing conditions, with inconsistent performance frequently reported in commercial settings. A key contribution of this review is the conceptual integration of the gut–liver–immune axis as a central regulatory network underlying additive functionality in carnivorous fish. This framework highlights the importance of mechanism-guided selection and scenario-based application rather than indiscriminate additive combination. Furthermore, emerging strategies, including precision amino acid delivery, fermentation engineering, smart delivery systems, and nutrigenomics, are critically evaluated in terms of their translational potential and limitations. Future research should prioritize large-scale field validation, cost–benefit optimization, and multi-omics integration to bridge the gap between mechanistic understanding and industrial application, thereby supporting the development of economically viable and environmentally sustainable largemouth bass aquaculture systems.
Zinc oxide nanoparticles (ZnO-NPs) represent a sustainable feed additive with potential anthelmintic effects and the ability to mitigate enteric methane (CH₄) emissions. This study evaluated the effects of ZnO-NPs as a commercial product (SkySpring Nanomaterials, Inc., Houston, USA) on dry matter digestibility (DMD), body weight, parasitological status, ruminal fermentation, enteric carbon dioxide (CO₂) and CH₄ emissions in lambs infected with the gastrointestinal nematode Haemonchus contortus. Twenty-four lambs were assigned to four groups (n = 6): control fed a basal diet (CON), control supplemented with ZnO-NPs (CON-ZnO-NP), infected fed a basal diet (INF), and infected supplemented with ZnO-NPs (INF-ZnO-NP). Infected groups received approximately 5000 third-stage larvae on day 0, while ZnO-NP supplementation started on day 1 and continued for 39 days. Enteric gas emissions were measured during the final nine days using open-circuit respiratory chambers. DMD was 6% lower in INF compared to CON, whereas supplementation increased DMD by 8% in INF-ZnO-NP relative to INF. Ruminal pH and ammonia nitrogen concentrations were significantly higher in infected groups than in uninfected groups. Faecal egg counts were reduced by 39.9–52.9% in INF-ZnO-NP compared with INF during the final week. ZnO-NP supplementation reduced CO₂ emissions by 12% and CH₄ emissions by 20% in infected lambs. Overall, ZnO-NPs reduced parasitic burden and enteric gas emissions while improving digestibility, demonstrating their potential as a functional feed additive under diverse farming conditions.
Enteric methane production in ruminants represents a significant contributor to greenhouse gas emissions and an important loss of dietary energy. Plant derived phytochemicals have emerged as promising natural agents capable of modulating rumen methanogenesis, including potential interactions with methyl coenzyme M reductase, the terminal enzyme involved in methane formation. This review examines the biochemical basis of rumen methanogenesis and highlights recent advances in computational approaches, including virtual screening, molecular docking, molecular dynamics simulations and quantitative structure activity relationship modelling, for identifying candidate phytochemical inhibitors of methyl coenzyme M reductase. These in silico tools can support the rapid screening and prioritisation of large phytochemical libraries, but their predictions require careful interpretation because binding affinity alone does not confirm biological efficacy in the rumen. The review therefore discusses the need for subsequent validation through in vitro rumen fermentation studies, controlled in vivo trials, dose optimisation, assessment of rumen fermentation responses and evaluation of animal performance. Overall, this review provides a molecular and computational framework for identifying potential phytochemical methane mitigation candidates, while emphasising that their translation into practical ruminant feeding strategies remains dependent on further nutritional, biological and farm level validation.
The supply of fishmeal is under growing pressure, and effective alternative protein sources are urgently needed. In this context, single-cell protein (SCP) has arisen as a compelling alternative, distinguished by high protein conversion efficiency, a well-balanced essential amino acid profile and environmental sustainability. This review synthesizes recent progress in bacterial, microalgae and fungal SCP production, alongside feeding studies in key aquaculture species. It demonstrates that judicious SCP inclusion can improve growth performance, feed efficiency, immune response and intestinal health, but efficacy is highly dependent on species traits, life stage and SCP source. Finally, this paper summarizes the challenges SCP faces in practical applications. It proposes strategies to advance its industrial development through strain selection, process optimization and precision feeding, thereby providing a theoretical basis and technical pathway for sustainable protein supply in aquaculture.
Soy protein concentrate (SPC) is a potential plant-protein ingredient for aquafeeds, but inadequate lysine availability may limit its nutritional value in formulated diets. This study evaluated the effects of lysine supplementation in SPC-based diets on growth performance, nutrient utilization, physiological responses, and tissue characteristics of hybrid sturgeon (Acipenser baerii ♀ × A. schrenckii ♂). Juveniles with an initial body weight of 8.0g were fed four isonitrogenous and isolipidic diets for 8 weeks: a fish meal (FM)-based control diet and three SPC-based diets supplemented with 0% (L0), 0.25% (L2.5), or 0.50% (L5) lysine. Relative to L0, L2.5 increased final body weight and weight gain rate, whereas feed conversion ratio and protein efficiency ratio did not differ significantly between the two groups. Increasing supplementation to 0.50% provided no additional growth benefit; L5 had poorer FCR and PER than L2.5. Whole-body proximate composition and amino acid profiles were unaffected by dietary treatment. The L5 group exhibited the highest hepatic MDA content and CAT activity, together with altered serum biochemical indices. In the intestine, L2.5 showed higher lipase activity and villus height than L0 and L5, whereas L5 exhibited lower trypsin activity, muscular layer thickness, and goblet cell abundance. Relative to L2.5, L5 also showed lower transcript levels of tight-junction- and immune-defense-related genes and higher expression of the pro-inflammatory genes il-8 and tnf-α. Muscle fiber density was higher in L2.5 than in L0 and L5, whereas L5 showed lower springiness and chewiness than L2.5. Overall, 0.25% supplemental lysine produced the most favorable growth, intestinal, and muscle responses among the SPC-based diets tested. Further dose–response studies are required to establish the dietary lysine requirement of hybrid sturgeon fed SPC-based diets.
L-carnitine serves as a critical regulator of fatty acid metabolism in fish, playing an indispensable role in their growth, development, and nutrient metabolism. In aquaculture systems, dietary L-carnitine supplementation has attracted considerable attention because of its potential to enhance growth performance, improve feed utilization efficiency, and optimize lipid metabolism. This article systematically reviews recent advances in the role of L-carnitine in fish growth regulation and lipid metabolism, with particular emphasis on its molecular mechanisms. Current findings demonstrate that L-carnitine has a positive effects on lipid metabolism regulation, primarily through activating the fatty acid β-oxidation pathway to facilitate long-chain fatty acid transport into mitochondria, thereby effectively modulating lipid metabolism. At a molecular level, L-carnitine exerts its physiological functions by regulating metabolic pathways such as the PPAR signaling pathway and the L-carnitine palmitoyltransferase (CPT) system. Despite the advances critical knowledge gaps remain regarding optimal dosage thresholds for different fish species, systematic evaluation of long-term supplementation effects, and precise molecular mechanisms-particularly its interactions with other nutrients. Moreover, recent studies indicate that excessive L-carnitine supplementation may cause metabolic disorders, reduce protein deposition efficiency, and even inhibit growth in certain fish species. These findings underscore the importance of considering species-specific differences, establishing precise dose-response relationships, and optimizing supplementation timing to fully understand L-carnitine potential. Such advances will provide a stronger scientific basis for precision nutrition strategies and the sustainable development of aquaculture.
This 56-day trial evaluated artemisinin (0, 4.5, 9.0, 13.5, 18.0, 22.5, 27.0mg/kg) in isonitrogenous, isolipidic high-lipid diets for juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂; initial body weight 18.54±0.09g). Fish were fed diets A1 (0mg/kg, control) through A7 (27.0mg/kg). The artemisinin-treated groups showed that weight gain % (WGR) and protein efficiency ratio (PER) rose then fell, peaking at A6; WGR in all treatments was significantly higher than the control. The feed conversion ratio (FCR) declined to A6 then rose. Artemisinin supplementation significantly reduced serum total cholesterol (TC) and triglycerides (TG) in certain treatment groups, significantly decreased low-density lipoprotein (LDL) in all treatment groups, and significantly increased high-density lipoprotein (HDL) in some treatment groups. They also decreased liver TC, TG and very low-density lipoprotein (VLDL), and enhanced lipoprotein lipase (LPL), hepatic lipase (HL) and adipose triglyceride lipase (ATGL) activities. Qualitative observation of Oil Red O staining showed a visible reduction in the number and size of lipid droplets in the liver with increasing artemisinin supplementation. Artemisinin upregulated the mRNA expressions of hsl, atgl and cpt1, and downregulated the mRNA expressions of fas, acc and srebp1 of liver. Artemisinin improved growth performance and hepatic lipid metabolism in juvenile hybrid grouper, and the optimal supplementation level was estimated to be 19.66mg/kg based on weight gain %.
Astragalus polysaccharides (APS) have been widely studied as immunostimulants in aquaculture, but their comprehensive effects on growth, immunity, intestinal microbiota, and disease resistance in largemouth bass (Micropterus salmoides) remain unclear. In this study, largemouth bass (2.7g) were fed diets supplemented with 0.0%, 0.1%, 0.2%, 0.4%, or 0.8% APS for 73 days, followed by an Aeromonas hydrophila challenge. The results indicated that dietary addition of 0.1%-0.4% APS significantly enhanced fish growth and antioxidant capacity, while alleviating inflammatory responses and enhancing immune-related gene expression in the spleen (P < 0.05). Furthermore, fish fed 0.1%–0.2% APS exhibited higher survival after A. hydrophila challenge (P < 0.05). Dietary supplementation with 0.1% APS also altered intestinal microbiota composition by increasing beneficial bacteria (e.g., Clostridium sensu stricto 1) and reducing potentially harmful bacteria (e.g., Achromobacter and Pedobacter). A broken-line regression analysis based on specific growth rate and cumulative mortality after A. hydrophila challenge indicated that the estimated optimal dietary APS level was approximately 0.09%–0.095% for largemouth bass. Overall, dietary APS supplementation improved growth performance, antioxidant status, immune responses, disease resistance, and intestinal microbiota composition in largemouth bass, suggesting its potential application as a functional feed additive in aquaculture.
