Feed & Additive Magazine Issue 3 April 2021

ISSUE FOCUS FEED & ADDITIVE MAGAZINE April 2021 31 with a mucus layer functions as the final barrier be- tween the luminal content and the underlying host tissue. There is proven effect of microbiome, espe- cially probiotics on gut integrity, thanks to • Direct secretion of metabolites and • Indirect modulation of gut microbiota. There are many components to maintain intestinal integrity: e.g. tight junctions (TJ), desmosomes, ad- hesion junctions, and gap junctions. TJ is a complex of several proteins also known as tight junction proteins that reside in the apical section of the epithelial cell. These proteins include both membrane bound and intracellular proteins that interact between adjacent cells, but also with the cytoskeleton in the cell. This helps stabilising the TJ, but also makes it possible for the cytoskeleton to regulate interactions between IEC. The review of the current knowledge of the most rel- evant gut health biomarkers for poultry production is summarized in this article and effect of the probiotic solution Bacillus subtilis DSM 29784 (Bs29784) on modulating these markers are also highlighted. The first approach is to do the macroscopical scor- ing of the intestine. Several methodologies exist but the one published by Teirlynck et al (2011) showed negative correlation with villus length and positive correlation with T-cell infiltration in dysbacteriosis condition. In our trial, a dietary challenge was in- duced by increasing NSP content of the feed with 20% rye inclusion. The Bacterial Enteritis Score was 2.0 for the control group and decreased to 1.0 with the supplementation of Bs29784. Then, microscopical evaluation (histomorpholo- gy) of the gut gives a precise state of the epithelial integrity and inflammation (Gholamiandehkordi et al, 2007). For instance, longer villi height (and then quantity of epithelial cells) is associated with higher body weight (Kraieski et al, 2017). On 42-day-old broilers, Bs29784 significantly increased villi length relative to control from 0.66 to 0.79 µm in the ile- um, and from 1.25 to 1.46 µm in the cecum. Looking at the microbiota from an ecological per- spective could provide insight into how to promote health by targeting this microbial community with dietary solutions. Microbiota will be as resilient as possible if the population is diverse and contains more bacteria with anti-inflammatory properties (butyrate producers like Ruminococcaceae and Lachnospirace- ae) and less opportunistic pathogens like Clostridi- um perfringens or Enterobacteriaceae (Salmonella or Escherichia coli). In a necrotic enteritis challenge model, Bs29784 group showed higher alpha-diversity than control birds with Chao and Shannon index. We also observed higher prevalence of Ruminococcace- ae (P>0.001) with the supplementation of Bs29784, especially for Faecalibacterium prausnitzii (+13.4%; P<0.001) that is known to be correlated with other gut health parameters such as villus length and CD3 area. In another trial where broilers were challenged with C. perfringens, we observed that the number of E. coli at 21 d and the number of C. perfringens at 28 d were significantly reduced in the Bs29784 group. Finally, some microbial metabolites can be linked to gut health. Nicotinic acid for instance activates the GPR109A receptor, which suppresses intestinal inflam- mation. We demonstrated that it increases cell prolifer- ation and wound healing in a Caco-2 in vitro model. An exploratory study on 13-day-old chicks showed that Bs29784 increased (P <0.01) the intestinal content of nicotinic acid in ileum and jejunum, revealing a mode of action through which it can improve gut health. This showed some very important gut health bio- markers that could be used for both research and practical purposes. We also demonstrated that these key markers can be measured to evaluate the consis- tent efficacy of Bs29784 in broilers.