Abstract: This study was conducted to determine the effects on performance and immune responses of Linwu ducks supplemented with high lysine-yielding Bacillus subtilis. The 200 and 41 days old female commercial Linwu ducklings were distributed randomly into four groups of 60 ducks each which were further replicated to three groups of 20 each. The ducks were placed on one of four dietary treatments: basal, basal with antibiotic (150 mg Aureomycin whose effective content was 15% per kg feed) and fed with basal diet but deleted lysine (0.15%) and respectively added 5x108 CFU and 5x1010 CFU Bacillus subtilis per kilogram feed. The trial lasted for 63 days. Average body weight gain for 63 days breeding was observed significantly increase in antibiotic-added group (p<0.05) but not showed in supplemented Bacillus subtilis groups. It was basically lying in the same level to average feed intake and feed conversion ratio as accessed from each group. Mortality experienced pronounced recession with Bacillus subtilis or Aureomycin addition. Breast meat, leg meat and liver relative weigh were greatly improved by fed with 5x1010 CFU kg-1 Bacillus subtilis supplemented diet, although, dressing percentage, semi-eviscerated percentage, eviscerated percentage and percentage of abdominal fat were unaffected. No marked significance was observed in serum profile, except for serum Total Protein (TP) increasing as the consequence of 5x1010 CFU kg-1 Bacillus subtilis supplement. Supplement 5x1010 CFU kg-1 Bacillus subtilis also increased crude protein proportion in meat. Amino acid percentages in meat varied differently between experimental treatments. Additionally, the results in the current research revealed that diet supplemented with Bacillus subtilis tended to markedly suppress IL-2 both in spleen and thymus compared with control. Dietary treatment with 5x1010 CFU kg-1 Bacillus subtilis addition or Aureomycin addition down regulated IL-18 in spleen when compared with control. Treatments did not induce any significant effects on INF-α, INF-γ, IL-1 and IL-10 gene expression both in thymus and spleen. It was concluded that dietary supplementation with these high lysine-yielding Bacillus subtilis showed promising effects as alternatives for antibiotics due to it had a favor to growth performance and slaughter performance and depression on inflammatory cytokines overproduction which was stimulated by pathogens.
Y.T. Xing, S.P. Wang, J.X. Fan, T. Yang, L.L. Li, B. Zhang and D.F. Xiao, 2014. High Lysine-Yielding Bacillus subtilis as a Promising Alternative to Antibiotic for its Effects on Performance and Immune Responses of Linwu Ducks. Journal of Animal and Veterinary Advances, 13: 355-364.