The potential probiotic role of <i>Lacticaseibacillus rhamnosus</i> on growth performance, gut health, and immune responses of weaned pigs

During the weaning period, piglets suffer from various challenges induced by changed trophic conditions, unstable immune systems, and exposure to unfamiliar environments accompanied by direct or indirect production losses. Supplementation of probiotics in a nursery diet has been considered an effective strategy that improves the growth rate and gut health of pigs. In swine production, lactic acid-producing bacteria (LAB), including Lactobacilli, are commonly used as prominent probiotics. Thus, the objective of this study was to evaluate the effects of dietary Lacticaseibacillus rhamnosus (LR), one of the Lactobacilli probiotics, on growth performance, frequency of diarrhea, nutrient digestibility, gut health, and immune responses of weaned pigs. A total of 48 pigs (6.51 ± 0.87kg; 28 d old) were allocated to 2 dietary treatments in a randomized complete block design (block: initial body weight). Dietary treatments were a basal nursery diet based on corn-soybean meal (CON) and CON + 0.02% LR (IDCC 3201; 2 × 109 CFU/g; Ildong Bioscience Co, Ltd, Seoul, Republic of Korea). The experiment was conducted for 4 wk. In this study, the LR group increased (P < 0.05) gain to feed ratio from d 1 to 7 compared with the CON group. Pigs fed LR had higher (P < 0.05) apparent total tract digestibility of dry matter, energy, and crude protein than those fed CON. The dietary LR decreased (P < 0.05) crypt depth in the duodenum and ileum compared with CON. The dietary LR upregulated ileal expression of the claudin-1 gene (P < 0.05) and tended to increase the claudin-2 gene (P = 0.089) while downregulated (P < 0.05) expression of tumor necrosis factor-α and interleukin-8 genes compared with CON. The LR group decreased (P < 0.05) platelet count on d 14 compared with the CON group. Furthermore, pigs fed LR had lower serum concentrations of the tumor necrosis factor-α on d 7 (P < 0.05) as well as interleukin-6 on d 7, 14, and 28 (P < 0.05) than those fed CON. This study suggests that the supplementation of 0.02% LR in the nursery diet can improve the growth performance and nutrient digestibility of weaned pigs by enhancing intestinal morphology, ileal gene expression of tight junction proteins and inflammatory cytokine, and systemic immune responses.