Alex H. L. Wan

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.

The present study was conducted to evaluate the effect of different dietary protein levels on digestive enzyme activities, nutrient assimilation as well as growth performance in striped catfish (Pangasianodon hypophthalmus). Fish were fed with four semi-purified formulated diets with increasing levels of protein: 30% (CP30), 35% (CP35), 40% (CP40) and 45% (CP45) for 12 weeks. At the end of the feed trial, the highest weight gain (29.88 g fish-1), specific growth rate (3.58%) and lower feed conversion ratio (1.91) were observed in fish that were fed with a 40% protein diet while CP30 treatment group had the poorest growth performance indicators (P<0.05). Proximate analysis revealed that fish fed with either CP40 (18.50%) or CP45 (19.33%) diets had the highest protein content in comparison to that fed CP30 (17.13%) and CP35 (17.00%) diets. Similarly, the highest body lipid content was CP35 (4.20%) treatment group and the lowest in CP40 (3.83%). The amino acid in the harvested fillets was also significantly higher (P<0.05) in both CP40 and CP45 dietary treatments. The increasing dietary protein level also elevated both protease and amylase activity, while lipase activity significantly decreased (P<0.05). The study revealed that a 40 % protein level diet produced from regional ingredients in the Middle East had yielded optimal growth performance and higher muscle quality in striped catfish.