Effects of dietary formic acid polymer supplementation on growth performance, blood parameters, and intestinal health in lipopolysaccharide-challenged broilers

Abstract

This experiment was performed to investigate the impacts of formic acid polymer (FAP) supplementation to the diet on the growth performance, blood metabolites, as well as intestinal barrier function related indicators of broilers under lipopolysaccharide (LPS) stimulation. A total of 450 1-day-old male Arbor Acres broilers with similar body weights were assigned to one of three experimental groups: control (CON) group, basal diet; LPS group, basal diet with LPS (1 mg/kg body weight) challenge; LPS+FAP group, basal diet supplemented with FAP (1,000 mg/kg) and LPS (1 mg/kg body weight) challenge. Each group had 6 replicates of 25 broilers. LPS was injected on days 17, 19, and 21. Samples were collected on day 21, 3 h post-challenge. The experiment lasted 21 days. LPS treatment reduced growth performance, immune function, and caused systemic inflammation, intestinal barrier damage, and microbiota dysbiosis in broilers. However, FAP supplementation significantly reversed these effects by reducing the feed-to-gain ratio and serum levels of interleukin (IL)-1β and tumor necrosis factor-α (P < 0.05), while increasing serum levels of complement C4, IL-10, and immunoglobulin M (P < 0.05). FAP also improved villus height, trefoil factor family, and mucin 2 levels, decreased caspase activities (P < 0.05), and reduced harmful bacteria while promoting beneficial bacteria. To sum up, supplementing 1,000 mg/kg of FAP to the diet effectively enhanced immune function, and mitigated the systemic inflammatory response and intestinal barrier damage caused by LPS, thereby improving broiler growth performance.

Keywords: broiler; formic acid; gut microbiota; inflammation; intestinal barrier.

FIGURE 1

Effects of dietary formic acid polymer (FAP) supplementation on plasma metabolites in broilers challenged with lipopolysaccharide (LPS). (A) TP, total protein; (B) ALB, albumin; (C) HDL-C, high-density lipoprotein cholesterol; (D) LDL-C, low-density lipoprotein cholesterol; (E) UREA, urea nitrogen; (F) TCHO, total cholesterol; (G) TG, triglycerides; (H) GLU, glucose. CON (basal diet, saline injection); LPS (basal diet, LPS-challenged); LPS+FAP (basal diet with the addition of 1,000 mg/kg FAP, LPS-challenged). A P-value < 0.05 was interpreted as indicating statistical significance. *P < 0.05, **P < 0.01, ^#0.05 ≤ P < 0.1. n = 6 for each treatment.

FIGURE 2

Effects of dietary formic acid polymer (FAP) supplementation on plasma supplements, immunoglobulins, and inflammatory cytokines in broilers challenged with lipopolysaccharide (LPS). (A) C3, complement C3; (B) C4, complement C4; (C) IgA, immunoglobulin A; (D) IgY, immunoglobulin Y; (E) IgM, immunoglobulin M; (F) IL-1β, interleukin-1β; (G) IL-6, interleukin-6; (H) TNF-α, tumor necrosis factor-α; (I) IL-10, interleukin-10. CON (basal diet, saline injection); LPS (basal diet, LPS-challenged); LPS+FAP (basal diet with the addition of 1,000 mg/kg FAP, LPS-challenged). A P-value < 0.05 was interpreted as indicating statistical significance. *P < 0.05, **P < 0.01, ***P < 0.001, ^#0.05 ≤ P < 0.1. n = 6 for each treatment.

FIGURE 3

Effects of dietary formic acid polymer (FAP) supplementation on intestinal morphology in broilers challenged with lipopolysaccharide (LPS). (A) Villus height; (B) Crypt depth; (C) Villus height/crypt depth. CON (basal diet, saline injection); LPS (basal diet, LPS-challenged); LPS+FAP (basal diet with the addition of 1,000 mg/kg FAP, LPS-challenged). A P-value < 0.05 was interpreted as indicating statistical significance. **P < 0.01, ***P < 0.001. n = 6 for each treatment.

FIGURE 4

Effects of dietary formic acid polymer (FAP) supplementation on intestinal barrier function and apoptosis in broilers challenged with lipopolysaccharide (LPS). (A) ZO-1, zonula occludens-1; (B) TFF, trefoil factor family; (C) MUC2, mucin 2; (D) TGF-α, transforming growth factor-α; (E) Caspase-9; (F) Caspase-8; (G) Caspase-3. CON (basal diet, saline injection); LPS (basal diet, LPS-challenged); LPS+FAP (basal diet with the addition of 1,000 mg/kg FAP, LPS-challenged). A P-value < 0.05 was interpreted as indicating statistical significance *P < 0.05, **P < 0.01, ***P < 0.001, ^#0.05 ≤ P < 0.10. n = 6 for each treatment.

FIGURE 5

Effects of dietary formic acid polymer (FAP) supplementation on cecal microbiota richness and diversity in broilers challenged with lipopolysaccharide (LPS). (A) Rarefaction curve tending to approach the asymptote indicated the sequence depth met the requirements for sequencing and analysis. (B) Rank abundance curve reflected the richness of bacterial community by the width of the curve in the horizontal direction. (C) Stem-and-leaf display was generated to depict shared and unique sequences among the treatments. (D) α diversity indexes, including Shannon, Simpson, Chao 1, and ACE indexes, were used to estimate bacterial community richness and diversity, and values are mean 6 standard error (N = 6). (E) The principal coordinate analysis (PCoA) profile of weighted Unifrac distance. CON (basal diet, saline injection); LPS (basal diet, LPS-challenged); LPS+FAP (basal diet with the addition of 1,000 mg/kg FAP, LPS-challenged). A P-value < 0.05 was interpreted as indicating statistical significance. *P < 0.05, **P < 0.01, # 0.05 ≤ P < 0.10. n = 6 for each treatment.

FIGURE 6

Effects of dietary formic acid polymer (FAP) supplementation on the relative abundance of cecal microbiota at the phylum level in broilers challenged with lipopolysaccharide (LPS). CON (basal diet, saline injection); LPS (basal diet, LPS-challenged); LPS+FAP (basal diet with the addition of 1,000 mg/kg FAP, LPS-challenged). n = 6 for each treatment.

FIGURE 7

Effects of dietary formic acid polymer (FAP) supplementation on the relative abundance of cecal microbiota at the genus level in broilers challenged with lipopolysaccharide (LPS). The phylogenetic tree created using the sequences from the top 25 genera. The inner circle color-coded branches represent the respective phylum, while the outer circle features a stacked bar chart displaying the relative abundance of each genus across different treatments. CON (basal diet, saline injection); LPS (basal diet, LPS-challenged); LPS+FAP (basal diet with the addition of 1,000 mg/kg FAP, LPS-challenged). n = 6 for each treatment.