Lactobacillus plantarum Attenuates Cadmium-Induced Intestinal Barrier Dysfunction and Systemic Toxicity in Broiler Chickens: Association with Calcium Homeostasis, PIEZO1 Expression, and Tight-Junction Integrity

Heavy metal pollution is a serious environmental concern worldwide. Cadmium is one of the most common and hazardous heavy metals and is known to impair intestinal barrier integrity. Therefore, this study was designed to evaluate the protective effects of Lactobacillus plantarum against cadmium chloride (CdCl2)-induced toxicity in chickens. A total of 120 one-day-old Arbor Acres broiler chickens were randomly divided into four equal groups (n = 30 birds/group). Following a 4-day acclimation period, the chickens were subjected to a 28-day feeding trial. The control group (CON) received a standard basal diet, the probiotic group (LB) received L. plantarum at 1 × 108 CFU/mL via oral gavage, the co-treatment group (LC) received L. plantarum at 1 × 108 CFU/mL together with CdCl2 at 80 mg/kg, and the toxin group (CD) received CdCl2 at 80 mg/kg. Cadmium exposure markedly increased mortality, reduced survival rates, elevated serum liver enzyme activities (p < 0.0001), increased cadmium accumulation in tissues (p < 0.05), and decreased body weight gain in chickens (p < 0.0001). Moreover, cadmium exposure was associated with altered tissue Ca2+ homeostasis, upregulation of PIEZO1 expression and impairment of the epithelial tight-junction proteins, including ZO-1, occludin, and claudin-1. In contrast, L. plantarum supplementation improved intestinal barrier integrity and restored intestinal morphology, including villus height and crypt depth, which were adversely affected by cadmium exposure. Collectively, L. plantarum supplementation attenuated cadmium-induced systemic and intestinal toxicity, as evidenced by multiple protective mechanisms, such as reduced mortality, decreased tissue cadmium accumulation (p < 0.05), improved biochemical parameters, and preservation of intestinal morphology and tight-junction integrity. These findings suggest that L. plantarum may provide a potential dietary strategy for mitigating cadmium toxicity in broiler chickens.