Probiotic Lactiplantibacillus plantarum improved growth performance of weaned pigs by enhancing intestinal health and modulating immune responses

The objective of this study was to evaluate the effects of dietary probiotic <italic>Lactiplantibacillus plantarum</italic> (<italic>Lactobacillus plantarum</italic>) on growth performance, nutrient digestibility, immune responses, and intestinal health of weaned pigs. In a randomize complete block design (block: initial body weight), a total of 40 weaned pigs (initial body weight: 6.93 ± 0.27 kg) were assigned to 2 dietary treatments (1 pig/pen; 10 replicates/treatment): 1) a basal weaner diet based on corn and soybean meal (CON) and 2) CON + 0.1% dietary probiotic <italic>L</italic>.<italic> plantarum </italic>(PRO). Pigs fed PRO had increased (<italic>p</italic> &lt; 0.05) body weight, average daily gain, and gain to feed ratio during the overall period than those fed CON. Pigs in PRO had greater (<italic>p</italic> &lt; 0.05) apparent ileal digestibility of crude protein than those in CON. However, there were no differences on apparent total tract digestibility of dry matter, crude protein, and energy between dietary treatments. The PRO group decreased (<italic>p</italic> &lt; 0.05) crypt depth in the duodenum compared with the CON group, but increased (<italic>p</italic> &lt; 0.05) number of goblet cells in the ileum. Pigs fed PRO had lower (<italic>p</italic> &lt; 0.05) serum cortisol on day 7 and number of white blood cells on day 21 than those fed CON, but higher (<italic>p</italic> &lt; 0.05) serum interleukin-6 on day 21. The PRO group upregulated (<italic>p </italic>&lt; 0.05) claudin-2, claudin-3, claudin-4, occludin, and mucin-1 genes expression in the ileum compared with the CON group. Pigs fed PRO had altered gut microbial composition by increasing (<italic>p</italic> &lt; 0.05) the relative abundance of genera <italic>Enterococcus</italic> and <italic>Pediococcus</italic> in fecal microbiota on day 7, genera <italic>Lactobacillus</italic> and <italic>Streptococcus </italic>in fecal microbiota on day 21, and genera <italic>Streptococcus </italic>and <italic>Turicibacter</italic> in jejunal microbiota on day 35 compared with pigs fed CON. Our findings suggest that supplementation of probiotic <italic>L</italic>.<italic> plantarum</italic> in weaner diets can enhance the growth performance of weaned pigs via modified intestinal health by improving intestinal morphology, upregulating tight junction protein genes expression, and altering microbial communities. Furthermore, the dietary probiotic <italic>L</italic>. <italic>plantarum</italic> modulated systemic immune responses and local inflammatory cytokine genes expression in the ileum of weaned pigs.