PS4-16. Effects of Bacillus Subtilis Combined with Plant Extracts on Systemic Immunity in Weanling Pigs

Abstract Our previous study demonstrated that dietary supplementation with Bacillus subtilis and plant extracts improved growth performance and reduced post-weaning (PW) diarrhea in pigs. The present study aimed to further investigate the effects of dietary supplementation with Bacillus subtilis and plant extracts combination on systemic immune and antioxidant responses in weanling pigs. A total of 240 pigs (6.12 ± 0.53 kg body weight BW) weaned at 19 ± 1 days were allotted to four dietary treatments in a randomized complete block design with initial BW as a blocking factor (6 pigs/pen; 10 replicates/treatment). The dietary treatments were: (1) Control (CON): Basal nursery diet; (2) BPS: CON + 500 mg/kg Bacillus subtilis and plant extracts; (3) BPD: CON + 1,000 mg/kg Bacillus subtilis and plant extracts; and (4) ATB: CON + 50 mg/kg carbadox (antibiotic). Pigs were fed the experimental diets for 28 days in two phases (phase 1: day 0 to 14; phase 2: day 15 to 28). Blood samples were collected from six pigs per treatment on days 0, 7, 14, 21, and 28 PW to assess serum inflammatory and antioxidant biomarkers, including C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), haptoglobin, glutathione peroxidase (GPx), and total antioxidant capacity (TAC), using commercial ELISA kits. Data were analyzed using the MIXED procedure of SAS, with pen as the experimental unit, diet as the fixed effect, and block as the random effect. On day 7 PW, serum CRP concentrations were lower (P 0.05) in BPS, BPD, and ATB compared with CON, and BPD significantly decreased TNF-α levels (P 0.05) compared with CON. On day 21 PW, serum haptoglobin was lowest (P 0.05) in BPD, while GPx activity was highest (P 0.05) and comparable to ATB. On day 28 PW, GPx activity remained highest (P 0.05) in BPD and ATB groups. In conclusion, dietary supplementation of Bacillus subtilis combined with plant extracts modulated systemic inflammation and enhanced antioxidant capacity during the early post-weaning period, suggesting potential as a natural alternative to antibiotic growth promoters in nursery pigs.