Nutritional strategies using synbiotics and organic acids to enhance piglet post-weaning growth and gut health

This study aimed to evaluate the effects of dietary supplementation with probiotics (PRO), synbiotics (SYN), and SYN + benzoic acid (SYP) on growth performance, stress response, nutrient digestibility, blood parameters, immune status, and intestinal health of weanling pigs. Four hundred weaned pigs (Landrace × Yorkshire × Duroc) were allocated to four treatment groups: control (basal diet), PRO (Bacillus licheniformis), SYN (Bacillus licheniformis + dietary fiber), and SYP. The feeding trial lasted for 28 days. Notably, pigs in the SYN and SYP groups showed greater average daily gain during phase 1 (p = 0.038), phase 2 (p = 0.008), and the overall period (p = 0.011) compared with those in the control group. Gain-to-feed ratio was also improved during phase 2 (p = 0.003) and the overall experimental period (p = 0.012). The SYP group demonstrated significantly improved dry matter digestibility during phase 2 (p < 0.05). Serum IL-1β concentrations tended to decrease in pigs fed SYN and SYP diets. In addition, SYN and SYP supplementation increased the concentration of the tight junction protein zona occludens-1 (ZO-1) in the jejunum (p = 0.022). Histological analysis showed greater villus height in the duodenum (p = 0.013) and jejunum (p = 0.038) of pigs fed SYN and SYP diets. Overall, dietary supplementation with synbiotics, particularly in combination with benzoic acid, improved growth performance and intestinal health in weanling pigs.