Betaine, a naturally occurring compound primarily derived from sugar beet by-products, has attracted increasing attention for its multifaceted roles in human and animal nutrition. Acting as both an osmolyte and a methyl group donor, betaine contributes to cellular hydration, methylation balance, antioxidant defense, and metabolic regulation. This review provides a comprehensive overview of betaine’s biological functions and its health-promoting effects across species. In humans, betaine supports hepatic function, cardiovascular health, renal protection, and physical performance, mainly by modulating homocysteine metabolism, lipid profiles, and oxidative stress. In animal production systems, it enhances growth, feed efficiency, reproductive performance, and resilience to heat stress, with species-specific applications in monogastrics, ruminants, aquaculture species, and companion animals. The review also explores the molecular mechanisms underlying betaine’s effects, including epigenetic regulation and mitochondrial function, and presents updated evidence on its biosynthesis, bioavailability, and nutrient interactions. Furthermore, the use of betaine derived from agro-industrial by-products aligns with the principles of the circular economy, promoting the sustainable reuse of valuable compounds within the agri-food chain. Despite promising findings, further research is needed to standardize effective dosages and clarify species-specific responses under different physiological and environmental conditions. Overall, betaine emerges as a promising and sustainable functional ingredient with wide-ranging applications in nutrition and health.

Closing the life cycle of European eel (Anguilla anguilla) in captivity is targeted to provide a sustainable, year-round supply of juveniles for aquaculture. Present focus is on the nutritional requirements during the larval first-feeding period. In this study, three experimental diets were tested on hatchery-produced European eel larvae from the onset of the first-feeding stage commencing 10 days post hatch (dph) until 28 dph. Larval mortality was recorded daily, while sampling was conducted at regular intervals to record larval biometrics and analyze the expression of genes related to digestion, appetite, feed intake and growth. Two periods of high mortality were identified: the first appeared shortly after introduction of feeds (10–12 dph), while the second occurred 20–24 dph, indicating the “point of no return”. This interpretation was supported at the molecular level by the expression of the gene encoding the “hunger hormone” ghrelin (ghrl) that peaked at 22 dph in all dietary trials, suggesting that most larvae were fasting. However, in larvae fed diet 3,ghrlexpression was downregulated beyond 22 dph, which indicated that those larvae were no longer starving at this stage, while upregulation of genes encoding the major digestive enzymes (try,tgl, andamyl2a) advocated their healthy development. Moreover, for larvae fed diet 3, the expression of those genes as well as genes for feed intake (pomca) and growth (gh) continued to increase towards 28 dph. These results together with the registered highest survival, largest dry weight increase, and enhanced biometrics (length and body area) pointed to diet 3 as the best-performing. As a whole, this first-feeding study represents a landmark being the first to document European eel larval growth and survival beyond the point of no return, providing novel insights into the molecular development of digestive functions during the first feeding stage.

Egg biochemical composition is among the main factors affecting offspring quality and survival during the yolk-sac stage, when larvae depend exclusively on yolk nutrients. These nutrients are primarily embedded in the developing oocytes during vitellogenesis. In aquaculture, assisted reproduction procedures may be applied enabling gamete production. For the European eel (Anguilla anguilla), reproductive treatment involves administration of pituitary extracts from carp (CPE) or salmon (SPE) to induce and sustain vitellogenesis. In the present study, we compared the influence of CPE and SPE treatments on offspring quality and composition as well as nutrient utilization during the yolk-sac stage. Thus, dry weight, proximal composition (total lipid, total protein), free amino acids, and fatty acids were assessed in eggs and larvae throughout the yolk-sac stage, where body and oil-droplet area were measured to estimate growth rate, oil-droplet utilization, and oil-droplet utilization efficiency. The results showed that CPE females spawned eggs with higher lipid and free amino acid contents. However, SPE females produced more buoyant eggs with higher fertilization rate as well as larger larvae with more energy reserves (estimated as oil-droplet area). Overall, general patterns of nutrient utilization were detected, such as the amount of total lipid and monounsaturated fatty acids decreasing from the egg stage and throughout the yolk-sac larval stage. On the contrary, essential fatty acids and free amino acids were retained. Notably, towards the end of the yolk-sac stage, the proximal composition and biometry of surviving larvae, from both treatments, were similar.

European eel, Anguilla anguilla, larval culture faces a bottleneck during the transition to exogenous feeding. To stimulate gut-priming, in the present study, prebiotics (AgriMOS, mannan-oligosaccharides, and β-(1,3 and 1,6)-poly-D-glucose), probiotics (Bactocell, Pediococcus acidilactici), and synbiotics (AgriMOS+Bactocell) were administered to European eel larvae during the endogenous prefeeding stage. Eel larvae were reared in 2L incubators with an initial stocking density of 200 larvae/L. Each treatment (pre-, pro-, synbiotics, and control), represented by 3 replicated incubators, was connected to a separate recirculating aquaculture system. The gut-priming agents were introduced directly into the rearing water. Results revealed increased mortality when larvae were introduced to synbiotics and impaired growth in connection to probiotics and synbiotics. Larvae receiving prebiotics showed similar survival and growth to larvae reared without gut-priming agents. The immune gene expression revealed a lag phase between maternally inherited protection (c3, igm, and il10) and the gradual buildup of the larvaes own immune system (il1β, irf7). The lack of treatment-related immune (c3, igm, il10, il1β, and irf7) and stress/repair (hsp70, hsp90) responses revealed an immature immuno-readiness. Digestion (try, ctra, ctrb, tgl, and amyl), food intake (cck), and appetite (ghrl)-related genes were expressed at basal levels already on 4days post-hatch, which combined with phenotypic plasticity of the appetite-regulating ghrelin (ghrl), indicated a prospective adaptive capability towards earlier maturation of the larval digestive capacity. Overall, we contemplate that the application of gut-priming agents in water has merit; however, as no beneficial effect was observed, we conclude that the regimen applied is not recommendable in the present form and needs to be customized for future eel larval culture. As such, water management strategies and rearing options need to be further explored to establish prefeeding and feeding regimens, targeting optimized culture conditions, and the production of healthy eel offspring.

The use of former foodstuff and by-products in cow diets could improve the environmental sustainability of livestock. However, knowledge about the effects of these feeds in ruminant diets on the quality of dairy products is lacking. This study investigated the effects of integrating wheat distillers’ grain with solubles (WDGS) and a former foodstuff product (FFP) into the diet of dairy cows on milk and cheese quality. The environmental impact of the two feeding systems has been evaluated by LCA. A double crossover design was set up with 84 Holstein cows, alternating a control diet and a circular one. In the circular diet, traditional feeds were partially replaced with 4 kg/d WDGS and 3 kg/d FFP. The results showed no effects on dry matter intake and milk yield, while fiber digestibility improved. A reduction in the milk fat content and a modification of the fatty acid profile of milk and cheese were observed. Conversely, cheese yield, composition, and sensory attributes were not affected. The environmental impact of the diet was significantly reduced in terms of land occupation, net fresh water, and global warming potential. These findings suggest that these feeds can be safely included in dairy cow diets. This approach could significantly contribute to reducing greenhouse gas emissions, enhancing the sustainability of the dairy system.

This study investigates the immunomodulatory effects of fish protein hydrolysates (FPHs) derived from Atlantic salmon ( Salmo salar ) by‐products using the Dicentrarchus labrax brain (DLB‐1) cell line. Utilizing aquaculture by‐products for FPH production offers significant potential in aquaculture, providing both economic benefits and a reduction on environmental impact. FPHs contain bioactive peptides with several biological properties, including health‐promoting, antioxidant, anti‐inflammatory, and antimicrobial activities. This study focused on the immunological properties of three FPHs, namely SS1, SS4, and SS5, obtained from salmon skin by‐products using enzymatic hydrolysis with trypsin, α chymotrypsin, and bromelain, respectively. Cytotoxicity assays showed that SS5 hydrolysate exhibited no toxic effects on DLB‐1 cells, even at high concentrations (up to 80 µg/mL), unlike SS1 and SS4 that showed a 50% cytotoxic concentration (CC ₅₀ ) of 7.0 and 11.8 µg/mL, respectively. Gene expression analysis revealed that SS1, SS4, and SS5 hydrolysates significantly upregulated the proinflammatory gene IL-1β ( p < 0.05), especially after LPS stimulation, indicating their potential to activate macrophages and modulate immune responses after bacterial infections. Interestingly, SS5 also significantly upregulated the anti‐inflammatory gene IL-10 when treated with LPS ( p < 0.05), suggesting its ability to regulate inflammation and balance immune responses. These results highlight the role of hydrolysis conditions, such as enzyme selection and peptide molecular weight, in determining the bioactivity of FPH. Moreover, the study suggests that smaller peptides with mass >1.0 and <2.0 kDa, particularly those produced with the bromelain enzyme in SS5, exhibit enhanced anti‐inflammatory properties. This research supports the use of FPH in promoting fish health by improving immune responses, and it contributes to sustainable aquaculture practices by transforming waste into valuable bioactive compounds, offering insights for future applications in functional feeds.