A comparative study of natural or artificial feed on physiological health and gut microbiota in mandarin fish (Siniperca chuatsi)

Abstract

Mandarin fish (Siniperca chuatsi) aquaculture faces sustainability challenges due to its reliance on live prey fish. Although artificial feed (AF) has ecological and economic advantages, the effects of artificial feed on physiological health and gut microbiota in mandarin fish are still unclear. This study aimed to determine the effects of AF on the digestive enzymes, antioxidative capacity, endoplasmic reticulum (ER) stress, inflammation, and gut microbiota in mandarin fish. Healthy and same-sized juvenile mandarin fish (average weight, 25.1 ± 0.1 g) were randomly divided into eight experimental cages (300 L) in quadruplicate (40 fish per cage). The fish in the control group were fed with Indian mrigal carp (Cirrhinus mrigala) with 17.2% wet-weight protein and 4.3% wet-weight lipid, while the fish in the AF group were supplied with an artificial diet. Fish were hand-fed to apparent satiation for 8 weeks. The results showed that the activities of digestive enzymes were 66–193% higher in the AF group compared with the control group. Artificial diet increased the content of malondialdehyde in the intestine of mandarin fish by 85%. Furthermore, the mRNA levels of ER stress-related genes, including X-box binding protein 1 (xbp1) and CCAAT/enhancer-binding protein-homologous protein (chop), were 63–79% higher in the AF group compared with the control group. Regarding cytokine expression, the mRNA levels of interleukin-8 (il-8) and tumor necrosis factor alpha (tnfα) were 62–418% higher in the AF group. In addition, artificial feed enhanced the α-diversity of the gut microbiota. The relative abundance of Lactococcus in the intestine was higher in the AF group. In conclusion, artificial feed enhanced the activities of digestive enzymes and the stability of the intestinal microecosystem while simultaneously inducing oxidative stress, ER stress, and inflammation in the intestine of mandarin fish. Thus, feed additives with antioxidant and immune-enhancing functions may be used in the process of artificial feed replacing live prey fish. This study provided theoretical guidance for the improvement of mandarin fish artificial feed.

Graphical Abstract