Dietary Supplementation of Lactiplantibacillus plantarum IDCC 3501 Modulated Immune Responses and Intestinal Health of Weaned Pigs

The weaning period is a crucial stage for piglets and can result in reduced growth performance and post-weaning diarrhea. In the swine industry, various feed additives have been widely evaluated to mitigate these challenges. Probiotics, especially lactic acid bacteria, are extensively studied as functional additives in swine production. However, the effects of probiotics are strain-dependent, and their underlying mechanisms are not fully understood. Therefore, this study evaluated the effects of dietary Lactiplantibacillus plantarum (L. plantarum) IDCC 3501 on growth performance, frequency of diarrhea, hematological parameters, biochemical parameters, intestinal morphology, immune responses, and gene expression of tight junction proteins and inflammatory cytokines in ileal tissue of weaned pigs. A total of 48 weaned pigs (initial body weight = 6.61 ± 0.85 kg; 28 days of age) were randomly assigned to two dietary treatments (four pigs per pen; six replicates per treatment) for 28 days. The dietary treatments included a basal nursery diet based on corn and soybean meal (CON) and the CON supplemented with 0.02% L. plantarum IDCC 3501 (LP; 2.4 × 106 CFU/g). Pigs fed LP had greater (P < 0.05) average daily gain from day 15 to 28 and tended to have greater (P = 0.057) feed efficiency from days 15 to 28 than those fed CON. Pigs fed LP tended to have a lower (P = 0.075) frequency of diarrhea during days 8 to 14 and had a lower (P < 0.05) hematocrit level on day 14. When LP was supplemented in the nursery diet, villus width and area in the jejunum tended to be greater (P = 0.081 and P = 0.072, respectively). The serum cortisol level was lower (P < 0.05) on day 7 when LP was fed. Also, dietary LP reduced (P < 0.05) concentrations of serum TNF-α and IL-6 on day 7, and IL-6 on day 14. At the end of the study, dietary LP supplementation upregulated (P < 0.05) expression of CLDN1, CLDN4, and IFNG genes, and downregulated (P < 0.05) expression of TNFA and IL8 genes. This study suggests that dietary LP supplementation may enhance growth performance of weaned pigs by mitigating post-weaning diarrhea, systemic stress and inflammatory responses, as well as improving intestinal barrier functions.