Polysaccharide Supplements from Millettia speciosa Champ. ex Benth Enhance Growth and Meat Quality in Wenchang Chickens

The polysaccharide of <i>Millettia speciosa Champ. ex Benth</i> (MSCP) has antioxidant properties, but its impact on chicken growth and development is not yet known. This study used chlortetracycline as a control to assess MCSP as a feed antibiotic substitute and its effects on Wenchang chicken production, slaughter performance, and meat quality. A total of 576 healthy 80-day-old Wenchang chickens were randomly allocated to six experimental groups. The control group (Control) received a basal diet, while the antibiotic group (CTC) was supplemented with 2 g/kg chlortetracycline (CTC). Four additional experimental groups were administered varying doses of MSCP: 400 mg/kg (MSCP₄₀₀), 800 mg/kg (MSCP₈₀₀), 1600 mg/kg (MSCP₁₆₀₀), and 3200 mg/kg (MSCP₃₂₀₀), respectively. The study discovered that incorporating MSCP and CTC into chicken diets significantly boosted the final body weight and average daily feed intake compared to the control group (<i>p</i> < 0.01), with MSCP notably enhancing average daily weight gain. With the addition of 800 mg/kg MSCP, chicken growth performance is comparable to that achieved with antibiotics in feed. However, it did not impact slaughtering performance (<i>p</i> > 0.05). In addition, MSCP significantly raised the pH after 24 h (<i>p</i> < 0.05) and decreased the yellowness (<i>p</i> < 0.01) of breast muscle. MSCP increased the essential amino acids (EAA) proportion in breast muscle (<i>p</i> < 0.05), EAA to nonessential amino acids (NEAA) ratio (<i>p</i> < 0.05), and diversity of fatty acids while decreasing C20:0 and increasing C18:2N6 and C22:1N9 content. Moreover, MSCP significantly reduced muscle fiber size (<i>p</i> < 0.01), increased fiber density (<i>p</i> < 0.01), boosted MYOD1 expression (<i>p</i> < 0.05), and decreased MSTN expression in breast muscle (<i>p</i> < 0.01). Overall, our study showed that supplementing the diet with MSCP, particularly at a dose of 800 mg/kg, enhanced growth, meat quality, muscle morphology, amino acid content, fatty acid composition, and gene expression related to muscle development in breast muscle. The results indicate that MSCP is a feed additive with the potential to replace antibiotics and improve meat quality, showing promising application potential.