Influence of Pleurotus sapidus fruiting bodies on the performance, cecal microbiome, and gene expression in the liver and breast muscle of broilers

Mushrooms, the fruiting bodies of edible fungi, are widely used as food for humans. However, their potential, as well as that of fungal mycelia, as feed components for poultry is less acknowledged. Recent studies have shown that feeding the vegetative mycelium of Pleurotus sapidus does not affect growth performance or nutrient digestibility and causes only minimal changes in the cecal microbiota structure, liver transcriptome, and plasma metabolome of broilers. The present study aimed to comprehensively investigate the effects of feeding the fruiting bodies of P. sapidus on performance metrics, ileal nutrient digestibility, cecal microbiota composition, cecal integrity, liver transcriptome, and the expression of genes involved in protein turnover in breast muscle of broilers. A total of 72 male, 1-day-old Cobb 500 broilers were randomly assigned to three groups and fed three distinct diets containing either 0 g (PSA-F0), 25 g (PSA-F25), or 50 g (PSA-F50) of freeze-dried P. sapidus fruiting bodies per kg diet in a 35-day, three-phase feeding regimen. Final body weights and weight gain during the finisher and the whole period were significantly lower in groups PSA-F50 and PSA-F25 compared to group PSA-F0 (P < 0.05). Feed intake during the finisher and the whole period tended to be lower in groups PSA-F50 and PSA-F25 compared to group PSA-F0 (P < 0.1). Average daily apparently digested amounts of most indispensable amino acids were lower in group PSA-F50 than in group PSA-F0 (P < 0.05). Cecal microbial α-diversity indicators (Chao1 and Richness) were significantly higher in the PSA-F50 group compared to the PSA-F0 group (P < 0.05), whereas β-diversity indicators were similar between groups. Taxonomic analysis showed a higher abundance of the class Bacilli and the species unknown_Erysipelatoclostridium and a lower abundance of the class Clostridia in the PSA-F50 group compared to the PSA-F0 group (P < 0.05). Concentrations of total and individual short-chain fatty acids, including acetic acid and propionic acid, in the cecal digesta were lower in the PSA-F50 group compared to the PSA-F0 group (P < 0.05). A total of 66 differentially expressed transcripts were identified in the liver between PSA-F50 and PSA-F0 groups based on filter criteria (FC > 1.3 or FC < -1.3, P < 0.05). The mRNA levels of genes involved in critical pathways such as protein synthesis and degradation—including the mammalian target of rapamycin pathway, myogenesis, the ubiquitin-proteasome system, autophagy-lysosomal pathway, and GCN2/eIF2α pathway—did not vary across the groups. Plasma lipopolysaccharide concentration was similar across all groups. The mRNA levels of CLDN3, MUC2, and MUC5AC were elevated in the PSA-F50 group compared to the PSA-F0 group (P < 0.05), while mRNA levels of CLDN5, OCLN, MUC13, and several pro-inflammatory genes in cecal mucosa remained unchanged across groups. The observed impairment in growth performance suggests that P. sapidus fruiting bodies cannot be recommended as dietary components for broilers at the tested doses. Considering the higher β-glucan content of fruiting bodies compared to vegetative mycelia, the negative effects observed on broiler performance may be associated with their β-glucan content.