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This study examined digestive enzyme activities and nutrient absorption capacities in the intestines of three commercially farmed fish species with different natural diets: Nile tilapia, common carp, and rainbow trout. Tilapia showed the highest carbohydrate digestion and glucose absorption capacity, followed by carp, then trout, reflecting their natural dietary preferences. When fed experimental diets with altered carbohydrate and protein ratios, carp and zebrafish adapted by upregulating digestive enzymes and glucose transporters in response to high-carbohydrate diets, while trout showed limited adaptive capacity for carbohydrate processing.
Why it matters
These findings have direct implications for developing cost-effective, sustainable plant-based fish feeds for aquaculture, which must double production in 20 years to meet demand. Understanding species-specific digestive limitations helps optimize feed formulations to match each fish's physiological capacity for processing different nutrient sources.
Understand the Science
⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Global aquaculture has grown significantly, but to maintain current consumption, supply must double over the next 20 years. Here, we characterised the digestive and absorptive capacities in the intestines of three commercially important, farmed fish species with varying natural diets: Nile tilapia (Oreochromis niloticus), common carp (Cyprinus carpio ), and rainbow trout (Oncorhynchus mykiss). Disaccharidase activity (maltase, sucrase) and sodium-dependent D-glucose absorption were highest in Nile tilapia, followed by common carp, and lowest in rainbow trout. We found regional intestinal differences in disaccharidase activity and SGLT1 expression in the three species. Aminopeptidase A (APA) and aminopeptidase N (APN) activities were typically highest in Nile tilapia. Intestinal expression of the neutral amino acid transporter B0AT1 was approx. double in tilapia and carp compared to trout. We also assessed common carp, zebrafish and Rainbow trout’s digestion profile when fed low-carbohydrate/high protein and high-carbohydrate/low-protein diets. Common carp and zebrafish adapted to high-carbohydrate diets by up-regulating both digestive enzymes and SGLT1. Common carp increased SGLT1 protein abundance 2.7-fold in the foregut and 4.6-fold in the hindgut. Rainbow trout increased disaccharidase activity but not SGLT1 expression in response to a high-carbohydrate diet. Both Rainbow trout and common carp down-regulated their APN activity but upregulated their B0AT1 expression 2-fold in response to increased dietary protein. These physiological limitations are critical considerations for formulating sustainable plant-based aquafeeds.