Effect of Lactobacillus paracasei LK01 on Growth Performance, Antioxidant Capacity, Immunity, Intestinal Health, and Serum Biochemical Indices in Broilers

This study aimed to investigate the effects of adding <i>L. paracasei</i> LK01 to the diet on the growth performance, antioxidant capacity, immunity, intestinal health, and serum biochemical indicators of broilers. This study selected 1080 one-day-old broiler chickens with similar body weight, and randomly divided them into six groups, with six replicates in each group and 30 chicks in each replicate. The chicks were fed (1) the basal diet (CON), (2) the basal diet with 10⁶ CFU/kg <i>L. paracasei</i> LK01(T1), (3) the basal diet with 10⁷ CFU/kg <i>L. paracasei</i> LK01(T2), (4) the basal diet with 10⁸ CFU/kg <i>L. paracasei</i> LK01(T3), (5) the basal diet with 10⁹ CFU/kg <i>L. paracasei</i> LK01(T4), and (6) the basal diet with 10¹⁰ CFU/kg <i>L. paracasei</i> LK01(T5). The experiment lasted for 42 days. In this study, compared with the CON group, the diet supplemented with <i>L. paracasei</i> significantly increased body weight from 1 to 21 days (<i>p</i> < 0.05). In addition, the 10⁶ CFU/kg <i>L. paracasei</i> LK01 group significantly reduced the activity of glutamic oxaloacetic transaminase and triglyceride levels; the 10⁷ CFU/kg,10⁸ CFU/kg, and 10⁹ CFU/kg <i>L. paracasei</i> LK01 groups also reduced serum uric acid and total cholesterol levels (<i>p</i> < 0.05). The experimental groups all had lower serum levels of malondialdehyde and interleukin-1β (<i>p</i> < 0.01). Except for the 10⁶ CFU/kg group, all experimental groups had significantly lower tumor necrosis factor-α, and the 10⁶ and 10⁷ CFU/kg groups had higher immunoglobulin M levels (<i>p</i> < 0.05). In addition, the 10⁶ CFU/kg group significantly reduced the depth of the ileocecal crypts and increased the villus-to-crypt ratio (V/C) of the jejunum and ileum. In addition, dietary supplementation with <i>L. paracasei</i> LK01 did not change the α diversity of the microbial community in the cecum, but significantly increased the proportion of <i>Bacteroides</i> (phylum) (<i>p</i> < 0.05). The 10⁶ CFU/kg group also significantly increased the abundance of beneficial bacteria such as <i>Ruminococcaceae</i> (genus), <i>Lachnospiraceae</i> (genus), and <i>Faecalibacterium</i> (genus) (<i>p</i> < 0.05). In summary, this study revealed that adding 10⁶ CFU/kg of <i>L. paracasei</i> LKO1 to broiler diets can improve their production performance, serum biochemical indicators, antioxidant, and immune capabilities, as well as cecal flora.