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A six‐week feeding trial was conducted to determine the effect of butyric acid (BA) inclusion in diet on performance of Barramundi (Lates calcarifer). Fish (12.0 ± 0.2 g) were fed with four experimental diets contained 0.0 (control), 2.5, 5.0 and 10.0 g BA/kg in triplicate. Fish fed on 5 and 10 g BA/kg diets had higher growth and total alkaline protease and lipase activities than the other treatments. Fillet protein content in BA‐supplemented groups was higher than the control. Liver catalase activity was highest in 2.5 g BA/kg group compared with the other groups. The values of liver superoxide dismutase activity and serum total protein concentration in 5 and 10 g BA/kg treatments were higher than those in the control (p < .05). Moreover, the highest and the lowest levels of serum lysozyme activity were noticed in the 10 g BA/kg and the control groups, respectively (p < .05). Also, the highest respiratory burst activity was observed in fish fed 5 g BA/kg feed. Supplementing diet with 2.5 or 5 g BA/kg resulted in higher serum haemolytic activity in fish compared with the other groups. The number of red and white blood cells increased in fish fed BA‐supplemented diets compared with the control (p < .05). In conclusion, the results of this study showed inclusion of BA at 5 g/kg diet in L. calcarifer juveniles improved growth and upgraded the general health condition by enhancing fish antioxidant enzyme activities and haemato‐immunological responses.

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An 80‐day feeding trial was conducted to evaluate the influence of different short‐term fasting and re‐feeding strategies on growth and physiological responses in yellowfin seabream, Acanthopagrus latus (2.4 ± 0.2 g) fingerlings. The fish were subjected to four different feeding regimes, and the control group fed four times daily to apparent satiation throughout the whole feeding period, while the other three groups were deprived for 2, 4 and 8 days followed by 8, 16 or 32 days of re‐feeding (F2R8, F4R16 and F8R32, respectively) in repeated cycles for 80 days. The fish in the control and F2R8 groups had the highest and the lowest total length, respectively (p < .05). Moreover, fish exposed to F4R16 had the highest hepatosomatic indices, while control fish had the lowest hepatosomatic indices (p < .05). Fish in the F2R8 group relatively had higher catalase and glutathione‐S‐transferase activities than other groups (p < .05). Furthermore, total protease, α‐amylase and alkaline phosphatase activities in the F4R16 and F8R32 were higher than the F2R4 and control groups (p < .05). Overall, this study showed that compensatory growth in weight and length and digestive enzyme activities were observed in the F4R16 and F8R32; however, the increase in the activity of antioxidant enzymes in the F8R32 group indicated that oxidative stress remained after 80 days of re‐feeding in the liver.

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Summary The capacity of sub‐yearling Siberian sturgeon (Acipenser baerii Brandt, 1869) (19.7 ± 0.8 g) to show compensatory growth was assessed for a 40‐day period for the effects of short‐term starvation and refeeding on growth, feeding performance and body composition. After acclimation, 25 experimental fish were randomly distributed among twelve 500‐L cylindrical fiberglass tanks with a flow‐through system. The fish were subjected to four different feeding regimes: control, which was fed four times daily to apparent satiation; T1: four periods of 2 days starvation alternating with 8 days re‐feeding; T2: two periods of 4 days starvation alternating with 16 days refeeding; T3: an 8 days starvation period followed by 32 days refeeding. At the end of the experiment, the deprived fish attained body weights comparable to those attained by the control fish. There were no differences in growth and feeding performances between the deprived and the control fish. Total protein and lipid contents of the control fish were significantly higher than that of T1 and T2 fish at the end of the experiment (P < 0.05). A significant difference in the energy content was observed between T2 and the control. Siberian sturgeon exhibited complete compensation, indicating a high ability of the deprived fish to grow sufficiently to fully compensate for weight loss during starvation. The results suggested that the feeding schedule involving starvation–refeeding cycles could be a promising feed management option for the culture of this species.

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A 6‐week study was conducted to assess the effect of dietary fishmeal (FM) replacement with Sargassum ilicifolium meal (SIM) at four substitution levels including 0 (control), 3% (S3), 6% (S6) and 9% (S9) on performance of Asian sea bass (Lates calcarifer) juveniles (initial mean body weight of 29.0 ± 1.0 g). Growth performance pronouncedly increased in SIM‐supplemented groups compared to the control (p < .05). Fish fed on the S6 diet had higher pancreatic digestive enzyme activities than other treatments. Supplementing diet with SIM remarkably enhanced red blood cell count compared to the control. Moreover, fish in the control and S3 groups had higher lymphocyte, but lower neutrophil percentages than the S6 and S9 treatments (p < .05). The greatest and the least amounts of the total protein and total immunoglobulins (Ig) in serum were found in the S6 and the control, respectively. The amount of alternative complement pathway activity in the serum of fish in the S9 group was higher than the other groups, whereas higher serum lysozyme activity was found in the S6 and S9 treatments compared to those in the control and S3 groups (p < .05). Total Ig content of the skin mucus in the S6 and S9 groups was higher than the control. The greatest and the least mucosal lysozyme activates were found in the S6 and control, respectively (p < .05). The liver superoxide dismutase activity in the S6 and S9 groups was higher than the other treatments (p < .05). The insulin‐like growth factor‐1 mRNA transcript abundance levels in the liver were greatest and the least in fish fed on the S9 and control, respectively. The expression of lysozyme gene, as indicated by an abundance of mRNA transcript for lysozyme, in the liver was higher in the S6 and S9 groups than the other groups (p < .05). Furthermore, fish fed the SIM‐incorporated diets had higher interlukine‐1β mRNA transcript abundance in the liver compared to the control (p < .05). Overall, according to the findings of this study 6% of dietary FM could be replaced with SIM to improve growth rate and health status in L. calcarifer juveniles.