Isolation and Identification of Duck Intestinal Probiotics and Their Effects on the Production and Immune Performance of Pekin Ducks

The purpose of this study was to investigate the effects of duck-derived probiotics added to drinking water on the production and immune performance of Pekin ducks. Two strains with good biological characteristics were isolated from the cecum of Pekin duck and identified as Lactiplantibacillus plantarum (L. plantarum) and Enterococcus faecalis (E. faecalis) by species identification. Then, a total of 90 uniformly sized and healthy 7-day-old Pekin ducks were randomly divided into three groups (six replicates per group, five ducks per replicate). Ducks in the control group were fed the basal diet (control group), and those in the experimental groups were fed the basal diet and supplemented with 1 × 107 CFU/mL L. plantarum (LP group) and E. faecalis (EF group) in drinking water, respectively. The supplementation of L. plantarum and E. faecalis in drinking water could significantly improve the average daily feed intake (ADFI) and average daily gain (ADG) of Pekin ducks, as well as the live weight, eviscerated weight, half-eviscerated weight, breast muscle weight, and leg muscle weight (p < 0.05). Compared with the control group, the duodenal villus height, duodenal V/C (villus height and crypt depth ratio), and ileal villus height were significantly increased in LP and EF groups (p < 0.05). Moreover, supplementing the L. plantarum and E. faecalis significantly improved the immune organ index and serum immunoglobulin A (IgA) content, and reduced the serum immunoglobulin G (IgG) content (p < 0.05). They also significantly decreased the number of pathogenic bacteria in the cecum of Pekin ducks and increased the number of Lactobacillus sp. (p < 0.05). This study indicated that adding duck-derived L. plantarum and E. faecalis can improve the production and immune performance of Pekin ducks, as well as enhance the structure of their gut microbiota and protect intestinal health. These findings deepen our understanding of the functions of duck-derived probiotics and provide a foundation for their use as feed additives.