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β-glucan is a well-documented feed additive for its potent immunostimulatory properties in many farmed fish species. This study examined how it can also be a promising growth promoter, modulate antioxidant enzyme activities, and act as an anti-stress agent in striped catfish (Pangasianodon hypophthalmus). A 12-week feeding experiment was untaken to determine the effects of dietary β-glucan supplementation at graded levels (0, 0.5, 1.0, and 1.5 g kg-1). Measured indicators suggest that a dietary inclusion level of 1.5 g kg-1 β-glucan gave the highest positive responses: weight gain (120.10 g fish-1), survival (98.30%), and lower FCR (1.70) (P<0.05). Whole body proximate analysis had only revealed that crude protein was significantly affected by the dietary inclusion of β-glucan (P<0.05), with the highest protein content (19.70%) being in fish that were fed with 1.5 g kg-1 β-glucan. Although other inclusion levels (i.e., 0.5 and 1 g kg-1) of β-glucan did not enhance body protein content (P>0.05). The assessment of fatty acid composition in muscle, liver, and adipose tissues showed modifications with the inclusion of β-glucan. Antioxidative-related enzyme activities (inc. catalase, glutathione peroxidase, and superoxide dismutase) that were measured in the liver had higher levels when fed with β-glucan inclusion diets (P<0.05). Following the feed trial, fish were subjected to crowding stress treatment. It was subsequently found that catfish fed with β-glucan-based diet groups had lower levels of blood stress-related indicators compared to the control group with no dietary β-glucan. The use of 1.5 g kg-1 of dietary β-glucan resulted in the lowest measured levels of cortisol (43.13 ng mL-1) and glucose (50.16 mg dL-1). This study has demonstrated that the dietary inclusion of β-glucan can have functional benefits beyond the immunological enhancements in striped catfish. Furthermore, its use can increase production levels and mitigate the stress associated with intensive farming practices. [ABSTRACT FROM AUTHOR]

The drop in temperature during the winter months can lead to a decrease in growth, induce metabolic stress, and increase mortality incidences. The present study evaluated the potential of functional feed additives in mitigating the negative impacts of winter‐rearing conditions in striped catfish (Pangasianodon hypophthalmus). Four test diets were evaluated over a twelve‐week feed trial: (1) zinc‐acetate (Zn‐acetate), (2) selenomethionine (Se‐Met), (3) β‐glucan, and (4) control with no added feed additive. The survival rate in the β‐glucan (95.00%) and Zn‐acetate (93.30%) dietary groups was higher than the control (78.30%) and Se‐Met (85.00%). Fish fed with the β‐glucan had the highest weight gain (20.75% increase), specific growth rate (13.75% increase), and lower feed conversion ratio (9.64 % decrease). However, feed additives did not influence the fatty acid profiles or whole‐body proximate composition. Although, Zn‐acetate and Se‐Met had higher body ash content. Serum cortisol and glucose levels were lower in β‐glucan and Zn‐acetate than in other treatment groups. All feed additives resulted in higher superoxide dismutase, glutathione peroxidase, and catalase activity in the liver and muscle. This study found that β‐glucan and zinc‐acetate can improve cold stress resistance and offer a sustainable strategy for catfish rearing over winter. [ABSTRACT FROM AUTHOR]