Effects of dietary supplementation of gallic tanninc acid on growth, intestinal digestive enzymes activity, innate immunity, morphology, and microbial composition of Cyprinus carpio
DESCRIPTION
In this study, we investigated the effects of gallic tannic acid (GTA) supplementation on the growth performance, intestinal digestive enzymes, morphology and microbial composition of common carp (Cyprinus carpio).
The basal diet (CK) was supplemented with 5 g/kg (TL), 10 g/kg (TM) and 20 g/kg (TH) for 6 weeks. Compared with the CK group, adding GTA (10 g/kg) significantly increased the weight gain rate (WG%), specific growth rate (SGR%) and body condition factor ratio (CF) of common carp (p < 0.05) and reduced the fish feed conversion ratio (FCR) (p < 0.05). GTA supplementation significantly increased digestive enzyme activity, including amylase (Ams), protease (Prt) and lipase (Lps) (p < 0.05).
Supplementing GTA can also enhance the innate immunity of common carp by reducing the activities of serum alanine aminotransferase (Alt), aspartate aminotransferase (Ast), malondialdehyde (Mda), and increasing catalase (Cat), total superoxide dismutase (Khorshidi, Paknejad, Sodagar, Hajimoradloo, & Shekarabi) levels (p < 0.05). Furthermore, the intestinal barrier is improved. Increases in villus length, goblet cell number, and occludin a (oclna) gene expression levels were observed. RT‒PCR results showed that GTA increasedthe expression levels of insulin-like growth factor 1 (igf1) and interleukin 4 (il4) and reduce the expression levels interleukin 6 (il6) mRNA in the fish intestine (p < 0.05).
Adding GTA to the diet significantly increased the abundance of beneficial bacteria Gemmobacter, Shinella and Actinobacteriota_unclassified, indirectly increased the activity of digestive enzymes and promoted the growth of fish. KEGG analysis shows that 10 g/kg of GTA can significantly enhance the lipid metabolism, carbohydrate metabolism, and amino acid metabolism pathways of the intestinal microbiota in fish (p < 0.05), thereby positively affecting the enhancement of intestinal digestive enzymes.
These results indicated that adding GTA to feed can effectively improve the growth performance of common carp by promoting intestinal health. We strongly recommend GTA at a concentration of 10 g/kg as a beneficial dietary supplement for common carp farming.
