Effects of Probiotic <i>Lactiplantibacillus plantarum</i> HJLP-1 on Growth Performance, Selected Antioxidant Capacity, Immune Function Indices in the Serum, and Cecal Microbiota in Broiler Chicken

This research study aimed to investigate the effects of <i>Lactiplantibacillus plantarum</i> (<i>L. plantarum</i>) on growth performance, oxidation resistance, immunity, and cecal microbiota in broilers. This work classed three hundred and sixty 1-day-old male broilers into three groups randomly, including a control group (CON, basal diet) and antibiotic (ANT, 75 mg kg⁻¹ chlortetracycline added into basal diet) and probiotic groups (LP, 5 × 10⁸ CFU kg⁻¹<i>Lactiplantibacillus plantarum</i> HJLP-1 contained within basal diet). Animals were then fed for 42 days, and each group comprised eight replicates with 15 broilers. Compared with CON, <i>L. plantarum</i> supplementation significantly improved the average daily weight gain (AWDG) (<i>p</i> < 0.05) while reducing the feed–gain ratio over the entire supplemental period (<i>p</i> < 0.05). Birds fed <i>L. plantarum</i> had markedly lower serum ammonia and xanthine oxidase levels (<i>p</i> < 0.05) than those in the ANT and CON groups. Significant improvements (<i>p</i> < 0.05) in superoxide dismutase, catalase, and serum IgM and IgY contents in broilers fed <i>L. plantarum</i> were also observed when compared with those in the CON and ANT groups. Both <i>L. plantarum</i> and antibiotics decreased pro-inflammatory factor IL-1β levels significantly (<i>p</i> < 0.05), while only <i>L. plantarum</i> promoted anti-inflammatory factor IL-10 levels in the serum (<i>p</i> < 0.05) compared with CON. <i>L. plantarum</i> (<i>p</i> < 0.05) increased acetic acid and butyric acid concentrations in cecal contents when compared to those in CON and ANT. Among the differences revealed via 16S rRNA analysis, <i>L. plantarum</i> markedly improved the community richness of the cecal microbiota. At the genus level, the butyric acid-producing bacteria <i>Ruminococcus</i> and <i>Lachnospiraceae</i> were found in higher relative abundance in samples of <i>L. plantarum</i>-treated birds. In conclusion, dietary <i>L. plantarum</i> supplementation promoted the growth and health of broilers, likely by inducing a shift in broiler gut microbiota toward short-chain fatty acid (SCFA)-producing bacteria. Therefore, <i>L. plantarum</i> has potential as an alternative to antibiotics in poultry breeding.