Echinacea purpurea polysaccharides regulate the intestinal microbiota and enhance immune function in broilers

Echinacea purpurea polysaccharide (EP), one of the main active components extracted from E. purpurea, exhibits immunomodulatory, anti-inflammatory, antioxidant, and intestinal mucosal protective effects. This study investigated the effects of EP on growth performance, antioxidant capacity, serum immune function, nutrient metabolism rate, and the composition of the intestinal microbiota in broilers. A total of 288 one-d-old Arbor Acres broilers (with an average body weight of 41.83 ± 0.32 g) were randomly allocated into four dietary treatments: a control group (CON; without EP) and three EP supplemented groups receiving 0.3%, 0.6%, or 0.9% EP designated as EPL, EPM, and EPH groups, respectively. The experimental feeding period lasted for 42 d. The results showed that, compared with the CON group, the addition of EP to the diet had no significant effect on average daily gain (ADG), the average daily feed intake (ADFI), or feed-to-gain ratio (F/G) of the broilers (P > 0.05), but did significantly reduced mortality, muscle drip loss rate, and shear force (P < 0.05). At 42 d of age, a notable increase in the serum total antioxidant capacity (T-AOC) levels and reduced malondialdehyde (MDA) levels in EPH group, compared with the CON group (P < 0.05). Compared with the CON group, the EPM group had higher high-density lipoprotein cholesterol (HDL-C) levels and lower serum total cholesterol (TC) and triglyceride (TG) levels (P < 0.05). Analysis of the caecal microbiota demonstrated that, compared with the CON group, supplementation with EP led to a marked increase in the proportional representation of beneficial bacterial populations (Alistipes, Ruminococcus_torques_group, and Bacteroides) while concurrently reducing the relative abundance of detrimental bacterial species (Streptococcus). Additionally, compared with the CON group, the addition of 0.6% EP elicited a significant increase in the concentration of short-chain fatty acids (SCFAs) in the caecal contents of the broilers both at 21 and 42 d (P < 0.05). The inclusion of EP in the diet substantially increased the nutrient metabolism rates (ether extract, crude ash, crude fibre, and calcium) of the broilers compared with those in the control group (P < 0.05). This study revealed the mechanisms by which EP enhanced broiler production performance, primarily through modulation of intestinal microbiota composition and promoting SCFA production. These changes, in turn, strengthened serum immune and antioxidant functions while improving nutrient metabolism rates. This ultimately translated into reduced mortality and improved meat quality under practical production conditions.