| Our previous research showed that Tachyplesin ?(TP?)had the functions of promoting the growth of chickens and improving immunity.It was found through PCR-DHPLC that it could increase the growth of some bacteria in the intestinal tract and inhibit the growth of other bacteria.Intestinal flora is closely related to nutrient metabolism,self-development,immunity and disease occurrence.Research and exploring new antibacterial agents are important measures to overcome the drawbacks of antibiotics.As a component of innate immunity,antimicrobial peptides are undoubtedly a promising leader in the development of new antibiotics.The application of antimicrobial peptides in animal husbandry production at home and abroad shows that it not only has antibacterial activity,participates in the recruitment of immune cells and regulates inflammatory response,but also has a selective promoting effect on beneficial bacteria in the intestinal flora.This study further explored the effect of TP? on growth performance and serum cytokines of SPF chickens.Simultaneously,the Illumina Miseq platform was used for double-end sequencing of 16 S rDNA V3-V4 region of caecum to reveal how TP? regulates intestinal flora and identify the different genus of bacteria,to provide data support for further enriching the regulation theory of chicken intestinal flora.The data of SPF chickens in the complete test period showed that body weight of TP? group were higher than that of control group,which showed a significant difference at 28 days(P < 0.05).Body weight gain was significantly higher in TP? group at 15-28 days and 29-42 days than in control group.The feed/gain of TP? group was significantly lower than that of control group at 15-28 d(P < 0.05).At the age of 42 days,the thymus index and the bursa of fabricius index in TP? group were significantly higher than those in control group(P < 0.05).The results showed that TP? could increase the average daily gain,feed utilization rate and immune function of SPF chickens.For Thl-type cytokines,TP? could significantly increase IL-12 level in serum at 28 d and 42 d,significantly increase IL-2 level of 28 d and IFN-? level of 42 d(P < 0.05),but had no significant effect on TNF-?(P > 0.05).For Th2-type cytokines,there was no significant difference in the levels of IL-4,IL-6,and IL-10 between the two groups at 28 days(P > 0.05).At 42 days,TP? significantly increased IL-4,IL-6,and IL-10 levels and decreased IL-1? level at 28 days(P < 0.05).Firstly,we analyzed the cecum intestinal flora of normal chickens and found that the dominant phylums were Firmicutes,Proteobacteria and Bacteroidetes,of which Firmicutes and Proteobacteria were abundant accounting for about 99% of the total abundance with the preponderance running through growth.At the genus level,Lactobacillus and Faecalibacterium had the highest average relative abundance.Butyricicoccus,Coprococcus,Ruminococcus and Dorea(P < 0.05)were the ones whose relative abundance gradually increased with the aging.The relative abundance decreased gradually including Odoribacter and Oscillospira(P < 0.05).Analysis of the caecum flora with TP? in vivo for 4 weeks and 6 weeks showed that the dominant bacteria genus and the phylum were not affected obviously by TP?.After 4 weeks of adding TP?,the superiority of dominant bacteria had not changed.Compared with control group,the relative abundance of butyric acid Butyricicoccus increased significantly(P < 0.05).After 6 weeks of adding TP?,the superiority of dominant bacteria had not changed.Compared with control group,the relative abundance of acetogenin Blautia increased significantly(P < 0.05).However,Coprococcus and Ruminococcus were significantly lower than control group(P < 0.05).In summary,our study further has confirmed that TP? can promote the growth of SPF chickens and the development of immune organs to improve growth performance.TP? could inhibit inflammatory cytokines and assist in enhancing the body's Th2-type immune response simultaneously.TP? in vivo did not damage the intestinal flora and could increase the relative abundance of short-chain fatty acids Butyricicoccus and Blautia significantly.TP ? may enhance body function by increasing the relative abundance of SCFAs-producing bacteria.This research data has enriched the theory of the formation and development of gut microbiota in chickens,and also provided data support for elucidating the regulatory function of TP? on chicken intestinal flora. |
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