Dietary supplementation with yeast cell walls affects feed conversion and gut transcriptome of broiler chickens

The study aimed at evaluating growth performance and gut transcriptome in broiler chickens fed a yeast-supplemented diet. A total of 576 male chickens were randomly allocated to 2 diets, i.e. C (control) or Y (with 250-500 g/ton of yeast fractions as SafMannan® according to the growth period). Growth was monitored until 44 d of age. At 42 d, the jejunum of 24 chickens (12 per diet) was sampled for wholetranscriptome profiling. Strand-specific RNAseq libraries were prepared and sequenced on Illumina HiSeq4000 following a 50 single-end strategy. Performance data were analysed with diet as the main factor of variability for individual (PROC GLM) or pen data (with pen as a random effect, PROC MIXED: SAS, 2013). A pairwise Differential Expression (DE) analysis was made using Deseq2 (adjusted p<0.10, fold change >1.5), followed by a Gene Set Enrichment Analysis (GSEA). The yeast supplementation did not significantly affect final live weight (2,959 and 2,968 g in birds fed diets C and Y, respectively), whereas it decreased feed intake (114 to 111 g/d; p<0.10) and improved feed conversion (1.74 to 1.70; p<0.01). As to gene expression, four genes were significantly overrepresented in broilers fed with the diet Y compared to C. When looking at genes under-represented in animals fed with the diet Y (no matter of the statistical significance), GSEA identified seven gene sets significantly enriched. A functional interpretation of these transcriptional differences showed that significant genes and gene sets play pivotal roles in immunity, NF-kB signalling, apoptosis, interferonmediated pathways, and inflammation processes. Due to the limited number of DE genes, clear-cut conclusions about the impact of yeast on gut transcriptome cannot be drawn. We hypothesize that yeast supplementation, besides improving feed conversion during growth, might improve anti-inflammatory state and immune responses of chickens against pathogens.