Differential gene expression analysis in broiler chickens in response to dietary larvae Mealworm meal inclusion

Recent studies on the exploitation of larvae meal inclusion in broiler chickens diet report a significant increase of breast muscle, carcass quality and growth performance. The purpose of this study was to investigate the effects of Mealworm (Tenebrio molitor, TM) meal inclusion in broiler chicken diet on global gene expression of four tissues, namely breast muscle, liver, jejunum and caecum. Isonitrogenous and isoenergetic diets were formulated with 0% (control group) and 15% (test group) of TM meal inclusion. 80 one-day-old male broiler chicks (Ross 708) were reared in 10 pens (eight birds/pen): the pens were divided in two groups including five experimental replicates for each diet. The birds were slaughtered at 53 days of age. The tissue samples were collected and stored in RNA Later solution (Ambion) for gene expression analysis. RNA-seq was carried out on Illumina NGS analyzer. The results showed that 117, 118, 119 and 182 RNA transcripts were upregulated and 120, 116, 168 and 126 RNA transcripts were downregulated in breast muscle, liver, jejunum and cecum respectively. In all tissues 25% of downregulated differentially expressed genes (DEG) had a foldchange> four; while the 25% of upregulated DEGs had a foldchange higher than four in breast and liver and>two in intestinal mucosa. A gene ontology analysis showed that only half of DEGs were involved in known biological processes including protein metabolism (30 DEGs), gene expression (30), signal transduction (15), and immune system (21). An expression pathway analysis with Reactome showed that the pathway with minor False Discovery Rate (FDR) was the striated muscle contraction in breast and the peptide chain elongation in the other tissues. The ubiquitin B gene (UBB), that plays an important role in protein's metabolism, was downregulated (-0.8) in breast and upregulated (þ0.57) in liver, whereas the expression of this gene did not change in intestinal mucosa. The differential expression of UBB might suggest an increase of non-lysosomal intracellular protein degradation related to a fast protein turnover in liver and a slow protein turnover in breast. In addition, the ribosomal protein (RPLP) profile, related to peptide chain elongation, was similar: -0.45 mean fold-change in breast and þ0.5 in liver while a moderated increase in intestinal mucosa was observed. No alterations in RNA expression were detected that could discourage the use of larvae mealworm inclusion in broiler chicken diet.