Effects of Antimicrobial Peptides Gal-13 on the Growth Performance, Intestinal Microbiota, Digestive Enzyme Activities, Intestinal Morphology, Antioxidative Activities, and Immunity of Broilers.

To evaluate the application effect of antimicrobial peptides Gal-13 (AMP Gal-13) instead of antibiotic feed additives, 90 7-day-old Ross 308 broilers were randomly divided into 3 groups. Group A was fed a basic diet as the control, and Groups B and C were supplemented with AMP Gal-13 (100 mg/kg and 200 mg/kg, respectively). After a 35-day feeding experiment, the weight and average daily gain (ADG) of the broilers in Group B were significantly higher than those of the broilers in Group A. The Enterococcus sp. and Escherichia coli counts in the ileum and cecum in Group A were significantly higher than those in Groups B and C, while the Lactic acid bacteria (LAB) and Bifidobacterium sp. counts were significantly lower. The amylase activity of the jejunum in Group B was significantly higher than that in Group A. The villus length (VL): crypt depth (CD) ratios of the jejunum and ileum in Group B were significantly higher than those in Group A. The glutathione peroxidase (GSH-Px) activities in the liver and serum in Groups B and C were significantly higher than those in Group A, while the malondialdehyde (MDA) activity was significantly lower. The titers of Newcastle disease virus (NDV)-specific antibodies were elevated significantly in Group B at the age of 42 days. Additionally, the weights of the spleen and thymus were significantly increased. The expression levels of Il-2, Il-6, Tgf-ß4, Tnf-α, and Mif in the spleen in Groups B and C were significantly downregulated to different degrees; Il-4 expression in Group B was significantly upregulated, while Ifn-γ expression in Group C was significantly upregulated. The results suggested that adding AMP Gal-13 to the diet could improve intestinal digestion, the antioxidant capacity, and immune function, ultimately promoting the growth of broilers.

Molecular mechanism of enhancing the immune effect of the Newcastle disease virus vaccine in broilers fed with Bacillus cereus PAS38.

The aim of this study was to explore the molecular mechanism of enhancing the immune effect of the Newcastle disease virus (NDV) vaccine in broilers fed with Bacillus cereus PAS38. The results showed that the NDV antibody titer of broilers in the treatment group supplemented with B. cereus PAS38 was higher than that of the control group, and the difference was significant at 28 days of age (P < 0.05). The spleen, thymus and bursa of fabricius of 42-day-old broilers were quickly collected to construct a differentially expressed gene library of suppression subtractive hybridization (SSH). A total of 31 immune-related differentially expressed genes were screened from three immune organs, of which 15 were up-regulated and 16 were down-regulated. After silencing the up-regulated genes MIF, CD74, DOCK2 and KLHL6, the expression levels of cytokines (Akirin2, NF-κB, IL-2, IL-4, IL-6, IFN-γ and TNF-α) in lymphocytes were reduced to varying degrees. B. cereus PAS38 might be involved in the proliferation, differentiation, activation, migration of B lymphocytes and vaccine antigen presentation by up-regulating the expression of MIF, CD74, DOCK2, KLHL6 and other genes. Moreover, it also stimulated plasma cells to produce immunoglobulins and specific antibodies, thereby improving the humoral immune function of broilers and enhancing the immune effect of the NDV vaccine.