Total saponins of Gynostemma pentaphyllum mitigate chronic heat stress-induced thymus and spleen inflammation in broilers via NF-κB pathway activation

Heat stress ( HS ) can induce inflammatory conditions in the immune organs of poultry, thereby affecting their immune functions. Gynostemma pentaphyllum total saponins ( GP ) are a natural plant active component with significant possess anti-inflammatory properties and exhibit immunomodulatory impacts. Thus, this study investigates GP’s effects on growth performance, thymus/spleen indices, serum biochemical markers, antioxidant enzyme activities in these organs, and transcriptional/protein expression of NF-kB pathway-related genes in cyclically HS broilers. A total of 200 broilers at 28 days of age were chosen for this experiment and randomly partitioned into five cohorts. The CON cohort was provided with a basal feed and reared in an environment with a normal temperature(24 ± 1 °C), while the HS, HSLGP, HSMGP and HSHGP cohorts were raised in a high-temperature environment (33 ± 1 °C, 8 h/d) with the basal diet fortified with 0, 200, 300 and 450 mg/kg GP, respectively. The results showed that compared with the CON cohort, the ADG and ADFI of broilers in the HS cohort were significantly reduced to 35 and 42 days ( P <0.05). GP exerts a positive influence on the growth traits of HS broilers by elevating ADG and ADFI, while concurrently reducing the F: G. GP improved the live weight, thymus, spleen index and tissue structure of HS broilers, and decreased the amounts of serum TC, LDL and LDH, while increasing the levels of TP, HDL, Ca and Mg ( P <0.05). Concurrently, GP supplementation enhanced the antioxidant enzyme activities in the thymus and spleen, increasing T-AOC, GSH-PX and T-SOD levels and significantly reducing MDA levels ( P <0.05). Additionally, compared with HS broilers, GP downregulated P65 protein levels, elevated the expression intensities of NF-kB genes and proteins, and triggered the expression activation of downstream inflammatory genes including HO-1, IKBα and Nrf2. In summary, GP modulates NF-kB pathway-associated gene/protein expression by suppressing inflammation, mitigates immune organ damage in broilers, and thereby enhances growth efficiency under HS.