Effects of Dietary Carbohydrate Levels on Growth Performance, Body Composition, Antioxidant Capacity, Immunity, and Liver Morphology in Oncorhynchus mykiss under Cage Culture with Flowing Freshwater

Abstract

The purpose of this study is to investigate the effects of dietary carbohydrate levels on growth performance, body composition, antioxidant capacity, immunity, and liver morphology in Oncorhynchus mykiss under cage culture with flowing freshwater. Fish (initial body weight 25.70 ± 0.24 g) were fed five isonitrogenous (420 g/kg protein) and isolipidic (150 g/kg lipid) diets containing 50.6, 102.1, 151.3, 200.9 and 251.8 g/kg carbohydrate levels, respectively. The results indicated that fish fed diets containing 50.6-200.9 g/kg carbohydrate showed significantly higher growth performance, feed utilization, and feed intake than those fed 251.8 g/kg dietary carbohydrate levels. Based on the analysis of the quadratic regression equation for weight gain rate, the appropriate dietary carbohydrate requirement of O. mykiss was estimated to be 126.2 g/kg. 251.8 g/kg carbohydrate level activated Nrf2-ARE signaling pathway, suppressed superoxide dismutase activity and total antioxidant capacity, and increased MDA content in the liver. Besides, fish fed a diet containing 251.8 g/kg carbohydrate showed a certain degree of hepatic sinus congestion and dilatation in the liver. Dietary 251.8 g/kg carbohydrate upregulated the mRNA transcription level of proinflammatory cytokines and downregulated the mRNA transcription level of lysozyme and complement 3. Whole-body compositions were not affected by dietary carbohydrate levels. In conclusion, 251.8 g/kg carbohydrate level suppressed the growth performance, antioxidant capacity and innate immunity, resulting in liver injury and inflammatory response of O. mykiss. A diet containing more than 200.9 g/kg carbohydrate is not efficiently utilized by O. mykiss under cage culture with flowing freshwater.

Exploring the effects of dietary inulin in rainbow trout fed a high-starch, 100% plant-based diet

“…We also studied the effects of the change in the CHO/protein ratio as well as the inulin factors on immunity actors in intestinal mucosa and liver. Indeed, the presence of anti-nutritional factors in the diet can induce innate immune response of epithelial cells and in the liver [93][94][95]. In this study, a signi cant decrease of plasma nitric oxide (NO) in sh fed with the high-starch diet was also observed.…”

“…While the use of anti-nutritional factors can led to mucosal in ammation [94], a high-starch diet in rainbow trout may also result in higher production of liver pro-in ammatory cytokines [95], the liver in teleost being known to be involved in immune responses in teleosts [101,102]. Interestingly, here, high starch diets induced a signi cant decrease of the il1b, il8, and tnfa genes, suggesting that reducing of the proportion of plantproteins may result in a decrease of cytokines responses in the liver.…”

Exploring the effects of dietary inulin in rainbow trout fed a high-starch, 100% plant-based diet

“…We also studied the effects of the change in the CHO/protein ratio as well as the inulin factors on immunity actors in intestinal mucosa and liver. Indeed, the presence of anti-nutritional factors in the diet can induce innate immune response of epithelial cells and in the liver [ 93 – 95 ]. In this study, a significant decrease of plasma nitric oxide (NO) in fish fed with the high-starch diet was also observed.…”

“…While the use of anti-nutritional factors can lead to mucosal inflammation [ 94 ], a high-starch diet in rainbow trout may also result in higher production of liver pro-inflammatory cytokines [ 95 ], the liver in teleost being known to be involved in immune responses in teleosts [ 98 , 99 ]. Interestingly, here, high starch diets induced a significant decrease of the il1b , il8 , and tnfa genes, suggesting that reducing of the proportion of plant-proteins may result in a decrease of cytokines responses in the liver.…”

Dietary Exogenous α-Amylase Modulates the Nutrient Digestibility, Digestive Enzyme Activity, Growth-Related Gene Expression, and Diet Degradation Rate of Olive Flounder (Paralichthys olivaceus)

“…The results of carbohydrate incorporation studies are largely controversial. One study has reported that the inoculation of more than 12.6%dietary carbohydrate reduces the growth performance of rainbow trout ( Oncorhynchus mykiss ) [ 7 ], whereas many other studies have demonstrated that a higher percentage of carbohydrates enhances the protein and energy retention in Siberian sturgeon ( Acipenser baerii ) [ 8 ] and O. mykiss [ 9 ]. Therefore, exogenous digestive enzyme supplementation in fish diets has garnered increasing attention in the aquaculture of Yangtze sturgeon ( A. dabryanus ) [ 10 ] and cachama ( Piaractus brachypomus ) [ 11 ] as it promotes carbohydrate digestion and assimilation in these fish.…”