Dandelion extract on growth performance, immunity, stress and infection resistance in common carp

Abstract

In the present study, the effect of supplementation with dandelion extract (DE) in common carp feed. Seven levels of DE supplementation to the basal diet were evaluated, i.e., 0 %, 0.5 %, 1 %, 2 %, 4 %, 7 %, and 10 % (50 % polysaccharide content), for a feeding period of 56 days. The addition of DE to the diet increased weight gain rate, specific growth rate,and protein efficiency ratio of common carp in DE2, DE3, DE4, DE5 and DE6 group. In contrast, it significantly reduced feed conversion ratio. Interestingly, DE supplementation did not have a significant effect on survival rate, condition factor, viscerosomatic index, and hepatosomatic index (P > 0.05). Moreover, DE supplementation improved the content of growth hormone (GH) and insulin-like growth factor (IGF-I) hormones in common carp serum, which was correlated with upregulation of genes coding for these two hormones in hepatopancreas (P < 0.05). Furthermore, DE supplementation increased the contents of total protein, albumin, and globulin in common carp, whilst reduced the contents of cholesterol, triglyceride, and urea nitrogen. Supplementation with DE promoted an increase in high-density lipoprotein cholesterol and a decrease in low density lipoprotein cholesterol contents. DE supplementation increased the activities of alysozyme, alkaline phosphatase, superoxide dismutase, catalase, glutathione peroxidase, and total antioxidant capacity, and the levels of complement 3 and complement 4. Furthermore, the activities of AST and ALT, and the contents of malondialdehyde and reactive oxygen species were reduced. In bacterial challenge tests with Aeromonas hydrophila, the mortality rate of common carp receiving supplementation with DE was lower. Collectively, DE supplementation improve growth performance, immunity, antioxidant capacity, gene expression, and the ability to withstand A. hydrophila infection in common carp. The recommended dosage of DE supplementation for the common carp diet is within the range of 5.42 %.