Potency of Lacticaseibacillus paracasei as an alternative to antibiotic growth promoter in broiler chicken challenged with avian pathogenic Escherichia coli

Background and Aim: The emergence of antibiotic-resistant bacteria due to the widespread use of antibiotic growth promoters (AGPs) necessitates the exploration of sustainable alternatives in poultry production. This study evaluated the efficacy of Lacticaseibacillus paracasei as a probiotic alternative to AGPs in broilers challenged with avian pathogenic Escherichia coli (APEC), with a focus on growth performance, antioxidant status, lipid metabolism, and hematological profiles. Materials and Methods: A total of 80 broiler chickens were randomly allocated into four groups: T0 (uninfected control), T1 (APEC-infected control), T2 (APEC + AGP, 0.1% zinc bacitracin), and T3 (APEC + probiotic, 0.5% L. paracasei). Treatments were administered from day 15 to 35 post-hatch, following a 2-week adaptation period. Performance indicators (feed conversion ratio [FCR], body weight gain [BWG], and feed efficiency [FE]), antioxidant parameters (superoxide dismutase [SOD] and malondialdehyde [MDA]), lipid profiles (cholesterol, HDL, and LDL), and hematological variables were assessed. Data were analyzed using analysis of variance with significance set at p < 0.05. Results: Probiotic supplementation significantly improved FCR, BWG, and FE (p < 0.05), with the T3 group achieving the most favorable outcomes. SOD activity was markedly higher, and MDA levels were reduced in probiotic-treated birds compared with the AGP and infected groups. Moreover, L. paracasei administration resulted in significant reductions in total cholesterol and LDL levels while maintaining moderate HDL concentrations. Hemoglobin and thrombocyte levels were modestly influenced, though overall hematological profiles remained stable across groups.