The Changes Of Gut Microbial Community In Chickens With TD And Effects Of LPS On The Tibial Bone Formation In Chickens

Tibial dyschondroplasia(TD)is a common bone disease in poultry.The etiology and pathogenesis of this disease remains unclear.The gut microbiota is a complex ecosystem which plays a very important role in the health of humans and animals.Many studies have linked diseases to the disorder of gut microbiota.However,little is known about whether gut microbiota plays a role in TD.Inflammation is an important defensive response of animals to against external stimuli.However,excessive inflammatory reactions can cause varying degrees of damage to animals.Numerous studies have linked inflammation to the development and progression of many diseases,including bone diseases.Previous studies have also shown that inflammation can inhibit the growth and development of bones.However,little is known about whether systemic inflammatory responses can lead to abnormal bone formation and even the bone diseases.And their underlying mechanisms are also unclear,especially in chickens.The purpose of these studies is to establish systemic TD model and inflammatory model in chickens using thiram and LPS respectively and taking the tibia as the research object to study whether the changes in gut microbiota can and inflammatory reaction affect the bone formation and link to the occurrence of bone diseases in chickens.1.Changes of gut microbiota in chickens with TD.The objective of this study was to investigate the diversity and composition of the microbial community in small and large intestine in TD chickens.TD in chickens was induced by feeding Thiram from day 3 and the dose was 100 mg/kg and the intestinal contents from healthy and TD chickens were collected on day 18.The V3-V4 region of 16 S rDNA was amplified and sequenced by high-throughput sequencing and the sequencing results were analyzed.The results showed that the abundance and diversity of gut microbiota in healthy broilers were higher than those in TD chickens,but the difference was not significant(P > 0.05).However,there was a significant difference in the composition of gut microbiota between healthy and TD chickens(P < 0.05).Compared with healthy broilers,the OTU abundance of microbiota associated with immunity and inflammation in TD chickens was significantly increased.The results showed that there were some differences in gut microbiota between healthy and TD chickens,which may related to immunity and inflammation.It provided a new thinking for the study of TD pathogenesis.2.Effects of LPS-induced systemic inflammatory response on bone formation in broilers.In this study,systemic inflammatory modeling in chickens were established by intraperitoneal injection of LPS at a dose of 2 mg/kg.The results showed an inefficient production performance and growth rate in LPS group.The number of platelets and inflammatory cells increased greatly in LPS group compared with control group.A significant increase of inflammatory factors,GC and RANKL was detected in LPS group,while OPG was decreased.Serum biochemical tests suggested abnormal liver function and disorder of Ca and P metabolism.We found that in LPS group,the number of blood vessels was reduced,while thrombus and chondrocyte nucleolysis were observed in tibial growth plate area by histopathological observation.mRNA and protein levels of various genes related to inflammation and bone formation were detected respectively.Compared with control group,the mRNA expression levels of TLR4,NF-?B,TF,TPO and its receptor C-MPL,MMP-9 and its inducer CD147 in LPS group were enhanced,while VEGFA was inhibited.In OPG / RANKL system,mRNA level of OPG was decreased in LPS group,while RANKL expression was enhanced.The results of protein levels showed an increase of NF-?B,CD147 and MMP-9 and a decrease both in VEGFA and OPG in LPS group.Therefore,we conclude that inflammation can inhibit bone modeling and bone remodeling processes,which is associated with the enhancement of thrombosis and the inhibition of angiogenesis,also related to the disorder of osteogenesis and the degeneration of bone ECM.In summary:1.The occurrence of TD in chickens may be related to the changes of gut microbiota.The abundance and diversity of gut microbiota in TD chickenss were lower than those in healthy chickens.Meanwhile,the immune and inflammation related gut microbiota were more abundant in TD chickens than in healthy chickens,which may be one of the potential causes of TD.2.Systemic inflammatory response has a negative impact on the process of tibial bone formation in chickens.This effect is achieved by inhibiting bone modeling and bone remodeling and promoting degeneration of ECM.