Dietary Hermetia illucens Larvae Replacement Alleviates Diarrhea and Improves Intestinal Barrier Function in Weaned Piglets Challenged With Enterotoxigenic Escherichia coli K88

Abstract

A high-quality protein substitute, <i>Hermetia illucens</i> (black soldier fly) larvae powder, is rich in protein and often used in animal feed. This study aimed to investigate the feasibility and optimal ratio of replacing fish meal with <i>H. illucens</i> larvae in weaned piglets and to demonstrate the effects on piglets' growth performance, intestinal microflora and immune performance. Forty-eight female weaned piglets were randomly classified into three groups. Each group consisted of eight pens (replicates), with two piglets per pen. Three groups containing different proportions of <i>H. illucens</i> larvae (0, 4, and 8%) were referred to as C, HI4, and HI8. We first designed a 28-day feeding experiment to detect growth performance; after that, the piglets were induced with oral gavage of enterotoxigenic <i>Escherichia coli</i> K88 (ETEC K88) and recording diarrhea on day 29 of the experiment. Samples were taken on the 32nd day to detect the effect of <i>H. illucens</i> larvae on the immune performance of the weaned piglets. <i>H. illucens</i> larvae replacement did not cause any obvious change in the growth performance nether in HI4 nor in HI8 of weaned piglets with 28 d feeding stage. <i>H. illucens</i> larvae could improve the intestinal health of weaned piglets by increasing the content of <i>Lactobacillus</i> and reducing the content of <i>Streptococcus</i>. Compared with C+K88 group, the diarrhea rate was attenuated for the <i>H. illucens</i> supplemented group. The integrity of ileum villi in HI4+K88 and HI8+K88 groups was better than that in C+K88 group, and the villi in C+K88 group were severely damaged. The expression of <i>IL-10, Occludin</i> and <i>Claudin-3</i> in the intestinal mucosa of the HI4+K88 group and HI8+K88 group were significantly increased (<i>P</i> < 0.05), and the expression of <i>TNF</i>-α was significantly decreased (<i>P</i> < 0.05) compared with the C+K88 group. The results of immunoblotting also validated that the same ETEC K88 treatment of weaned piglets enhanced the expression of tight junction protein in the intestinal mucosa of the <i>H. illucens</i> addition group. ETEC-induced diarrhea will be reduced by the diet of weaned piglets containing <i>H. illucens</i> larvae, ameliorating the immune performance of piglets. Our results indicates that the optimal dosage of <i>H. illucens</i> replacement in weaned piglets is 4%.