Metabolomic changes and enhanced digestibility with algae (Spirulina platensis) derived polysaccharides supplementation in broilers

Abstract

The objective of this study was to investigate the effects of algae (Spirulina platensis)-derived polysaccharides (ADPs) on performance, digestibility, intestinal histomorphology, digestive enzyme activities, and metabolomic profiles in broiler chickens. A total of 320 one-day-old Ross 308 mixed-sex broilers were randomly allocated to 5 dietary treatments comprising 0 (Control), 1500, 3000, 4500, and 6000 mg ADPs/kg in a completely randomized design. Each treatment included 4 replications, with 16 birds per replicate. The feeding trial lasted 42 days, encompassing starter (1–10 days), grower (11–24 days), and finisher (25–42 days) phases. The results demonstrated that dietary ADPs supplementation at 3000 mg/kg significantly enhanced (P < 0.05) body weight gain and improved feed conversion ratio during the overall period (1–42 days). In addition, supplementation with 1500–4500 mg/kg ADPs significantly improved (P < 0.05) in vitro crude protein digestibility (period 2) and apparent metabolizable energy (periods 2 and 3). Meanwhile, in vivo digestibility was also enhanced by ADPs supplementation, with significant improvements (P < 0.05) in dry matter (period 2) and crude protein (periods 2 and 3) digestibility. Histomorphological analysis revealed that ADPs supplementation at 1500–6000 mg/kg significantly increased (P < 0.05) villus height, villus width, villus height-to-crypt depth ratio, and villus surface area throughout the small intestine. Additionally, digestive enzyme activities, including amylase, lipase, and protease, were significantly elevated (P < 0.05) in broilers supplemented 3000–4500 mg/kg ADPs. Metabolomic analysis identified significant alterations in liver and breast muscle metabolites, with 194 differentially expressed metabolites in the liver and 134 in the breast, primarily associated with amino acid metabolism pathways. In the liver, the most affected pathways included lysine degradation, glycine-serine-threonine metabolism, and arginine biosynthesis. In the breast muscle, key pathways included phenylalanine-tyrosine-tryptophan biosynthesis, glycine-serine-threonine metabolism, and valine-leucine-isoleucine biosynthesis. Regarding principal component analysis demonstrated distinct clustering between control and ADPs-treated groups, indicating notable metabolic shifts. These findings suggest that the supplementation of ADPs from S. platensis enhances nutrient digestibility, intestinal morphology, digestive enzyme activity, and key metabolic pathways, ultimately supporting broiler growth performance. Based on the comprehensive findings of this study, dietary supplementation with ADPs at 3000 mg/kg is recommended as the optimal level.