Chondroitin sulfate modulates gut microbiota to improve bone metabolism and reduce locomotion problems in...

Chondroitin sulfate (CS) is known to promote bone health, but its effects on skeletal development and gut microbiota in yellow-feathered broilers remain largely unexplored. This study aimed to evaluate the effects of CS on bone health, growth performance, and intestinal flora in broilers. A total of 720 one-d-old Jinling yellow-feathered broilers (initial body weight 37.0 ± 0.5 g) were randomly divided into four treatment groups, each with nine replicates of 20 birds. The control group was fed a basal diet (CON), while the experimental group was supplemented with low (LCS), medium (MCS), or high CS (HCS) levels (0.05%, 0.15%, or 0.30%) for 30 d. Samples were collected every 10 d during a supplementation period of 30 d and again at 63 d to investigate the effect of early supplementation of CS on bone development later in life. Chondroitin sulfate supplementation improved broiler growth performance only at the beginning of the study. Compared with the CON group, the MCS group significantly increased tibial weight and length, and improved mid-segment geometric parameters, including vertical wall thickness (WTv), cross-sectional moment of inertia (CSMI), and cross-sectional area (CSA) (P < 0.05). The MCS group optimized bone trabecular structure, increased bone volume/tissue volume (BV/TV) and trabeculae thickness (Tb.Th) (P < 0.05); promoted new bone formation, and enhanced bone Ca and P deposition, compared with the CON. Chondroitin sulphate supplementation significantly decreased serum bone resorption markers tartrate resistant acid phosphatase (TRAP), elevated bone formation markers bone specific alkaline phosphatase (BALP) at 30 d, and down-regulated the expression levels of bone resorption-related genes (TRAP and RANKL) (P < 0.05). Compared with the CON group, the MCS group significantly increased the abundance of p_Bacillota_A_368345, Faecalibacterium, and Brotaphodocola (P < 0.05); and decreased the abundance of harmful bacterial genera. Functional prediction showed that the MCS group down-regulated some pro-inflammatory and tricarboxylic acid (TCA) cycle-related pathways and up-regulated carbohydrate degradation pathways (P < 0.05), compared with the CON group. In conclusion, CS supplementation improved bone quality, and altered the composition of intestinal flora during broiler growth.