Impact of stickwater soluble fraction supplementation on growth performance, body composition, digestibility, and digestive enzyme activity in beluga sturgeon (Huso huso) larvae

This study aimed to investigate the effects of stickwater (SW) on growth performance, digestibility, and intestinal structure in great sturgeon (Huso huso) larvae. A total of 1440 sturgeon larvae were selected and randomly assigned to 12 tanks (four treatments with three replicates each). The larvae were fed experimental diets containing 0% (SW0), 0.5% (SW0.5), 1.5% (SW1.5), and 2.5% (SW2.5) SW. No significant differences were observed in final weight, weight gain, or protein efficiency ratio among treatments (p > 0.05). However, a significant difference was found in specific growth rate (SGR) and feed conversion ratio (FCR) among treatments (p < 0.05), with SGR showing a positive linear relationship with SW content in the diets. There was no significant difference in feed intake (FI) among treatments (p > 0.05). The highest fillet fat content was recorded in the SW0 group, which was significantly different from the other treatments (p < 0.05). The highest trypsin activities were found in the SW2.5 group (p < 0.05). Lipase activity was higher in SW-containing diets compared with the control group (SW0) (p < 0.05). The highest feed consumption rate within short periods (10–30 min) was measured in the SW0.5 group, which was significantly different from SW0 (p < 0.05). The highest protein digestibility was observed in the SW2.5 group (p > 0.05), while fat digestibility was higher in the SW-containing diet groups than in the control group (p < 0.05). The maximum length of intestinal villi and muscle thickness were measured in the fish fed the 1.5% SW diet, which showed a significant difference compared with the SW0 group (p < 0.05). According to the results of the polynomial regression analysis, the 1.5% stickwater level led to the best growth performance. Overall, the inclusion of 0.5% to 1.5% stickwater in the diets of great sturgeon larvae enhanced feed attractiveness, improved growth performance, and increased digestibility.