Effects of dietary Brassica rapa L. polysaccharide on growth performance, immune and antioxidant functions and intestinal flora of yellow-feathered quail

This study aimed to explore the impact of Brassica rapa L. polysaccharides (BRP) on the growth, immune response, antioxidant capacity, and cecal microbiota in yellow-feathered quails. A total of 250 one-day-old yellow-feathered quails, evenly divided by sex, were randomly assigned to five groups, with each group comprising ten replicates of five quails each. The control group (CON) received a basic diet, while the antibiotic control group (CTC) was fed a basic diet supplemented with chlortetracycline (0.05 g/kg). BRP was administered at concentrations of 0.25 g/kg (Low dose BRP, LBRP), 0.5 g/kg (Medium dose BRP, MBRP), and 1 g/kg (High dose BRP, HBRP). The duration of the experiment was 42 days. The results indicated that, compared to the CON group, the final body weight of quails in the MBRP group significantly increased (P < 0.05), and there was a significant difference in body weight between the LBRP group and the CTC group (P < 0.05). At 21 days of age, the average weights of the thymus and bursa of Fabricius in the MBRP group were significantly greater than those in the CON group (P < 0.05), with no significant difference observed when compared to the CTC group (P > 0.05); at 42 days of age, the average weight of the thymus in the MBRP group was significantly greater than that in the CON group (P < 0.05), with no significant difference observed compared to the CTC group (P > 0.05). At 21 days of age, the levels of IgA and IgG in the MBRP group were significantly elevated compared to the CON group (P < 0.05), with no significant difference noted compared to the CTC group (P > 0.05). Additionally, the MBRP group showed significant increases in CAT, T-SOD, and GSH-Px levels (P < 0.05) compared to the CON group; the levels of IL-1β and TNF-α were significantly reduced (P < 0.05), and the level of IL-10 was significantly elevated (P < 0.05) compared to the CON group. Furthermore, 16 S rRNA sequencing revealed that BRP supplementation increased the populations of beneficial cecal bacteria such as Lactococcus, Weissella, Parabacteroides, and norank_f_Ruminococcaceae, and decreased the population of the harmful bacterium Campylobacter, indicating that BRP modulates the microbial community structure in the cecum of yellow-feathered quails. In summary, BRP enhanced the growth performance, serum immunoglobulin levels, antioxidant functions, and improved the intestinal microbiota in yellow-feathered quails.