Growth performance, intestinal microbiota and immune response of grass carp fed isonitrogenous and isoenergetic diets containing faba bean extracts

Abstract

Functionally active components of faba bean (Vicia faba, FB) are known to improve the muscle texture and growth performance of grass carp (Ctenopharyngodon idellus), but this has not yet been proven by feeding trials using isonitrogenous and isoenergetic diets. Here, we formulated isonitrogenous and isoenergetic diets containing four types of FB extracts and examined their effects on the weight gain, textural quality, intestinal microbiota, metabolic enzymes and immune response of grass carp by a 100-day feeding trial. An isonitrogenous and isoenergetic diet with no FB extracts (control) and whole FB were also used. Compared to the control, the FB water extract diet increased weight gain, muscle hardness and chewiness, intestinal microbiota diversity, the activity of metabolic enzymes including lipase (LP), glucose-6-phosphatase (G-6-P), acetyl-CoA and succinate dehydrogenase (SDH) (P < 0.05). The FB alcohol extract diet also increased weight gain, intestinal microbiota diversity, but the total cholesterol (TC) and triglycerides (TG) contents were also increased (P < 0.05). The FB protein extract and FB residues diets had negative and no effects on weight gain, respectively, and caused intestinal microbiota disorder. FB water and alcohol extracts enhanced intestinal amino acids metabolism, whereas FB water extract and residues enhanced intestinal carbohydrate metabolism. These results further extend previous findings that FB water and alcohol extracts contain most functionally active components of FB, opening up the possibility that these extracts can be used as functional feed additives for freshwater fish.