Intestinal Immune Cell Populations, Barrier Function, and Microbiomes in Broilers Fed a Diet Supplemented with Chlorella vulgaris

SIMPLE SUMMARY: Microalgae have a broad nutritional composition of proteins, lipids, and bioactive compounds such as polysaccharides, carotenoids, and chlorophyll. Even at low inclusion levels, Chlorella vulgaris (CV) is a promising sustainable feed additive because of its positive effects on the nutritional and functional properties of broiler chickens. These features may play a vital role in the early stage of birds as intestinal and immune maturation can lead to improved gut development and production in later stages. Therefore, in this study, we investigated whether incorporating CV into the diet of 10-day-old broilers would enhance their growth performance, gut functional characteristics, and bacterial communities. ABSTRACT: This study aimed to evaluate the effects of dietary Chlorella vulgaris (CV) on the distribution of immune cells, intestinal morphology, intestinal barrier function, antioxidant markers, and the cecal microbiome in 10-day-old broiler chickens. A total of 120 day-old Ross 308 male broiler chicks were assigned to two dietary treatments using a randomized complete block design, with body weight as the blocking factor. Birds fed a diet containing CV showed an increase in CD4(+) T cells (p < 0.05) compared to those fed the control diet. The relative mRNA expression of intestinal epithelial barrier function-related markers (occludin and avian β-defensin 5) was elevated (p < 0.05) in the CV-supplemented group compared to the control group. The alpha diversity indices (Chao1 and observed features) of the cecal microbiome in 10-day-old birds increased (p < 0.05), indicating higher richness within the cecal bacterial community. In the microbiome analysis, enriched genera abundance of Clostridium ASF356 and Coriobacteriaceae CHKCI002 was observed in birds fed the diet containing CV compared to those fed the control diet. Taken together, dietary CV supplementation might alter intestinal barrier function, immunity, and microbiomes in 10-day-old broiler chickens.