Supplementation of Yellow River carp diet with lutein and ferrous fumarate: Growth performance, digestive enzyme activity, skin pigmentation, and intestinal microbiota

In this study, the effect of the diet with lutein and ferrous fumarate on Yellow River carp ( Cyprinus carpio ) was studied, aiming to evaluate skin pigmentation, intestinal digestive enzymes, intestinal microbial diversity, and growth performance. Three experimental diets, including a control group, a lutein group (150mg/kg lutein), and a lutein and ferrous fumarate mixture group (150mg/kg lutein and 100mg/kg ferrous fumarate), were designed. The carp (N=135; 25.0±2.0g) were fed with experimental diets for 42 days. The results showed that the intestosomatic index (ISI) and viscerosomatic index (VSI) of the carp fed with lutein and ferrous fumarate were increased, accompanied by significant changes in body color, with the higher value of blue (b ), color difference (ΔE) and chroma (Ch ) compared with control group (P <0.05). Meanwhile, the higher activity of amylase, lipase, and trypsin were observed in the mixture group (P<0.05). High-throughput sequencing and Venn diagrams revealed that lutein or ferrous fumarate has obvious effects on the intestinal microbiota community of carp. The abundance of Actinobacteria and Flavobacterium was significantly increased in the carp fed with the mixture group compared with the control group. In conclusion, the addition of lutein and ferrous fumarate to the feed can change the skin pigmentation and intestinal microbial composition of Yellow River carp, thereby enhancing the coloring effect and digestive function of the fish. These findings provide valuable insights for optimizing feed formulation and aquaculture management, which can contribute to the improvement of the quality and farming efficiency of Yellow River carp.