In-feed resin acids reduce matrix metalloproteinase activity in the ileal mucosa of healthy broilers without inducing major effects on the gut microbiota

Abstract

The chicken gut is constantly exposed to harmful molecules and microorganisms which endanger the integrity of the intestinal wall. Strengthening intestinal mucosal integrity is a key target for feed additives that aim to promote intestinal health in broilers. Recently, dietary inclusion of resin-based products has been shown to increase broiler performance. However, the mode of action is still largely unexplored. Coniferous resin acids are known for their anti-microbial, anti-inflammatory and wound-healing properties, all properties that might support broiler intestinal health. In the current study, the effect of pure resin acids on broiler intestinal health was explored. Ross 308 broilers were fed a diet supplemented with coniferous resin acids for 22 days, after which the effect on both the intestinal microbiota as well as on the intestinal tissue morphology and activity of host collagenases was assessed. Dietary inclusion of resin acids did not alter the morphology of the healthy intestine and only minor effects on the intestinal microbiota were observed. However, resin acids-supplementation reduced both duodenal inflammatory T cell infiltration and small intestinal matrix metalloproteinase (MMP) activity towards collagen type I and type IV. Reduced breakdown of collagen type I and IV might indicate a protective effect of resin acids on intestinal barrier integrity by preservation of the basal membrane and the extracellular matrix. Further studies are needed to explore the protective effects of resin acids on broiler intestinal health under sub-optimal conditions and to elaborate our knowledge on the mechanisms behind the observed effects.

Figure 1

Alpha diversity of the microbial community from birds fed a control or a resin acids-supplemented diet. Observed: observed OTUs, Chao1: estimated OTU richness and Shannon: estimated community diversity.

Figure 2

PCoA plot of the microbiota from birds fed a control or resin acids-supplemented diet. Principle coordinate analysis (PCoA) plot of Bray–Curtis dissimilarities. Each point represents a single chicken microbiome. Significant separation of ileal microbial communities were revealed using ANOSIM (p = 0.002). This difference was less pronounced in the caecal microbiota (p = 0.055).

Figure 3

Relative abundance at phylum level in the ileum or caecum. Relative abundance (%) of the 4 most abundant phyla in the ileum or caecum from birds fed either the control diet or resin acids-supplemented diet.

Figure 4

Relative gelatin, collagen type I and collagen type IV degrading activity in small intestinal tissue. Duodenal (A–C), jejunal (D–F) or ileal (G–I) intestinal tissue lysates from either control birds or resin acids fed birds were incubated for 10 h with fluorescently labelled gelatin (A, D and G), collagen type I (B, E and h) or collagen type IV (C, F and I). Breakdown of the fluorescently labelled substrate results in an increase of fluorescence which is proportional to the substrate degrading activity of the sample. Data represent the mean (± standard deviation). FU: relative fluorescence units after 10 h incubation. *p < 0.05, **p < 0.01.

Figure 5

Effect of resin acids-supplementation on ileal gelatinolytic enzymes. Ileal tissue lysates from either the control group or the resin acids-supplemented group were pooled and subjected to gelatin zymography. Gelatinolytic enzymes are observed as clear bands of digested gelatin. Control tissue shows three different gelatinolytic bands, whereas only one band was observed in the ileal tissue lysate from birds fed the resin acids-containing diet.