Potential utility of dietary formate supplementation in facilitating growth performance and intestinal health for juvenile Songpu mirror carp (Cyprinus carpio Songpu)

This research was designed to assess the impacts of sodium formate on the growth performance, blood biochemical parameters, and intestinal health of Songpu mirror carp ( Cyprinus carpio Songpu ). Four isonitrogenous and isolipidic diets supplemented with varying concentrations of sodium formate (0 %, 0.5 %, 1 %, and 1.5 %, corresponding name: C0, FA1, FA2 FA3) were fed with an initial body weight of 6.61 ± 0.02 g for 8 weeks. Our results showed that the weight gain rate and specific growth rate initially trended upward, followed by a decline with increasing sodium formate in diets. The highest value occurred in the FA1 group, significantly exceeding that of the C0 group. By contrast, the FA1 group had a substantially lower feed conversion ratio than the C0 group. Among the serum indicators, the glucose content in the FA1 group was notably greater than that in other groups, while triglyceride levels were significantly reduced in FA1 group. Protease activity in the midgut was significantly enhanced in the FA1 group. In addition, the FA1 group showed a marked increase in the expression of sod, together with nrf2 and cat gene expressions, compared with the control group. In terms of intestinal immunity, 0.5 % sodium formate significantly regulated the expression of the zo-1 gene. The highest abundance of the phylum firmicutes was found in the 0.5 % sodium formate-treated group at the phylum level, while a higher abundance of Lactococcus lactis was found in the 0.5 % sodium formate-treated group at the genus level. In conclusion, 0.5 % sodium formate was identified as the optimal inclusion level in the diet.