| Summary: | To increase the current knowledge about the relationship between nutritional status and the digestive capacity of Siberian sturgeon (Acipenser baerii), we addressed the effect of starvation-refeeding and macronutrient composition on growth parameters and key digestive enzyme activities in A. baerii. Acipenser baerii juveniles were fed four different diets for 3 weeks, then starved for 2 weeks and allowed to refed for 5 weeks with the same diets. Another group of fish were fed 10 weeks with the corresponding diets. Among 10-week fed fish, high-protein diets promoted higher body weight values, while the lowest specific growth rate was observed in fish fed a low-protein, medium-carbohydrate, high-lipid diet (p < .05). At the end of the experiment, in fish refed for 5 weeks following a feeding-starvation cycle and in 10-week fed animals, the higher levels of blood glucose, triglycerides and cholesterol were found in fish fed low-protein diets (p < .05). In all treatments, 2 weeks of starvation decreased α-amylase activity in the intestine (p < .05), while 4 days of refeeding increased lipase (p > .05) and α-amylase activity in the intestine as well as pepsin in the stomach (p < .05). Our findings suggest that A. baerii maintains a high capacity to digest proteins and lipids after 2 weeks of starvation and that α-amylase can be used as an indicator of the nutritional status in fish submitted to starvation-refeeding cycles. Indeed, refeeding with high-protein and CHO:L ratio diets after starvation could improve the growth rate of A. baerii in culture.
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