Immune-biochemical responses of beluga larvae (Huso huso) fed by different levels of fish factory stickwater

This study was conducted to investigate the effects of stickwater (SW) (from fishmeal factories) on growth performance, immune system, and blood indicators on Huso huso larvae. Four experimental diets were prepared including the following: 0 (control, SW0), 0.5 (SW0.5), 1.5 (SW1.5), and 2.5 (SW2.5) % SW. A total number of 1440 larvae (0.12 ± 0.007 g) were selected 10 days after starting live feeding and were randomly stored in rearing tanks (120 larvae per tank). The fish were fed 6 times a day during the feeding trial. At the end of experiment, the highest weight gain (24.42 g) and specific growth rate (6.26%) were observed in SW0.5 (p ≤ 0.05). Moreover, SW1.5 treatment showed the best FCR (0.8) and PER (2.41%), although other treatments did not differ significantly. Total serum protein, albumin, and triglyceride levels increased by adding SW to the diet. The highest levels of total protein and albumin were seen in SW1.5 and SW2.5, respectively. There was a significant difference in triglyceride and the highest level was observed in SW1.5 treatment (p ≤ 0.05). Dietary stickwater did not significantly influence cholesterol, glucose, ALT, and ALP concentrations (p ≥ 0.05). The highest level of lysozyme enzyme activity was in SW0.5 and SW1.5, which showed a significant difference with the treatment without stickwater (p ≤ 0.05). Also, the presence of stickwater in the diet increased the level of serum immunoglobulin, but this increase did not cause a significant difference (p ≤ 0.05). The present study showed that adding stickwater (0.5 to 1.5%) to Beluga larvae’s diet improves their growth performance and some innate immune and serum biochemical parameters.