Effects of Fe (II)-chelating hairtail protein hydrolysates on the immune characteristics and intestinal microorganisms in loach (Misgurnus anguillicaudatus)

Abstract

To study the effects of Fe (II)-chelating hairtail protein hydrolysates [Fe (II)-HPH] on digestive enzymes, non-specific immunity and intestinal microbial community in loach, a total of 300 healthy loaches were selected. After adaptive feeding for one week, loaches were randomly assigned to five treatment groups with different concentration (0, 0.5, 1, 2, and 4 g/kg, respectively) of Fe (II)-HPH supplement added to feed. On the 40 d, assessment of digestive enzymes and non-specific immune indices were performed by collecting venous blood. Distribution of fluorescein isothiocyanate (FITC)-labeled Fe (II)-HPH in loach body was evaluated by live body imaging, and changes in the microbial community in the intestinal tract were detected by high-throughput sequencing. Results showed that enzymes activities of amylase, pepsin, and catalase (CAT) were significantly different (P<0.01 or P<0.05) in the group where concentration of Fe (II)-HPH in feed was 1 g/kg. Significant differences (P<0.01 or P<0.05) in enzymes activities of lipase, superoxide dismutase (SOD), lysozyme and malondialdehyde (MDA) were observed in the group where concentration of Fe (II)-HPH in feed was 2 g/kg. By tracing FITC which labelled Fe (II)-HPH, it was found that Fe (II)-HPH could stay in loach body for more than 8 h, and mainly distributed in the liver and gallbladder by analyzing the fluorescence intensity. The composition of intestinal microbiomes varied as Fe (II)-HPH concentration changed. Lactobacillus and Bacillus of the intestinal flora increased significantly. Fe (II)-HPH is proved to be a potential feed additive to enhance non-specific immunity and improve intestinal health in loach.

Keywords

• Loach (misgurnus anguillicaudatus)
• Fe (II)-chelating hairtail protein hydrolysates [Fe (II)-HPH]
• Non-Specific immunity
• Intestinal microorganisms