Effects of Compound Probiotics on Growth Performance, Serum Biochemical and Immune Indices, Antioxidant Capacity, and Intestinal Tissue Morphology of Shaoxing Duck

SIMPLE SUMMARY: The Chinese duck industry volume accounts for about 80% of the world’s total. Feed is the largest duck production cost; meeting feed requirements is important for successful duck farming. As feed additives, compound probiotics play an important role in duck production. This experiment was conducted to investigate the effects of compound probiotics (CP, composed of B. subtilis and B. Licheniformis ≥ 6.0 × 10(8) CFU/g) on growth performance, serum biochemical and immune indices, antioxidant capacity, and the intestinal tissue morphology of Shaoxing ducks. Results showed that the compound probiotics improved the growth performance, increased serum biochemical and immune indices, increased antioxidant capacity, and improved the intestinal tissue morphology of Shaoxing ducks; different day ages had different effects. This study provides a theoretical basis for the application of compound probiotics in the production of ducks and a reference basis for the development of green feed additives. ABSTRACT: This experiment was conducted to investigate the effects of compound probiotics on growth performance, serum biochemical and immune indices, antioxidant capacity, and the intestinal tissue morphology of Shaoxing ducks. A total of 640 1-day-old healthy Shaoxing ducks of similar body weight were randomly divided into two treatment groups with eight replicates each and forty ducks per replicate. The ducks were fed a basal diet (Ctrl) or a basal diet supplemented with 0.15% compound probiotics (CP) for 125 d. The results revealed that the live body weight (BW; day 85 and 125) and the average daily gain (ADG; 28–85 and 85–125 d) of the CP group were significantly higher (p < 0.05) than those of the Ctrl group. In the CP group, total protein and total cholesterol contents were significantly increased (p < 0.05) on days 28 and 85, while triglyceride and low-density lipoprotein contents were significantly decreased (p < 0.05) on day 85. Furthermore, interferon-γ content was significantly increased (p < 0.05) in the CP group on days 28, 85, and 125. Interleukin-2 content was significantly increased (p < 0.05) in the CP group on days 28 and 85. Interleukin-4 content was significantly decreased (p < 0.05) in the CP group on day 85. Moreover, in the CP group, superoxide dismutase content was significantly increased (p < 0.05) on days 28 and 125, and glutathione peroxidase content was significantly increased (p < 0.05) on day 125. The crypt depth (CD) in the duodenum of the CP group was significantly decreased (p < 0.05) on days 28 and 125, whereas the villus height (VH) in the jejunum of the CP group was significantly increased (p < 0.05) on days 85 and 125. The VH/CD ratio in the ileum of the CP group was significantly increased (p < 0.05) on days 28 and 85. The VH in the ileum of the CP group was significantly increased (p < 0.05) on day 28. The CD in the ileum of the CP group was significantly decreased (p < 0.05) on day 28. In summary, the compound probiotics improved the growth performance, increased serum biochemical and immune indices, increased antioxidant capacity, and improved the intestinal tissue morphology of Shaoxing ducks.