Insights into broilers’ gut microbiota fed with phosphorus, calcium and phytase supplemented diets

Background: Phytase supplementation in broiler diets is a common strategy to improve phosphorus (P) digestibility and to reduce its loss by excretion. An enhanced P availability, and its concomitant supplementation with calcium (Ca), can affect the composition of the microbial community in the digestive tract of broilers. Here, we aim to distinguish the effects of mineral P, Ca and phytase on the composition of microbial communities in the gastrointestinal tract (GIT) of broiler chickens.Results: Statistical differences were observed between digesta and mucosa samples for each GIT section. However? The analyses of 56 individual birds showed a high microbial composition variability within the replicates of the same diet. The average similarity within replicates of digesta and mucosa samples across all diets ranged from 29-81% in crop, 18-48% in ileum and 16-38% in caeca. Broilers fed a diet only supplemented with Ca had the lowest body weight gain and feed conversation values and the lowest microbial diversity, while all? diets supplemented with P showed the best performance results. An effect of each diet on crop mucosa was observed, however, similar results were not obtained from digesta samples. Microbial communities colonizing the ileum mucosa samples showed an effect of P supplementation. Caeca-derived samples showed the highest microbial diversity when compared to the other sections. Prominent OTUs were related to genus Faecalibacterium and Pseudoflavonifractor, known by its influence on gut health and as butyrate producers. Conclusions: Each diet affected microbial communities within individual sections, however, no diet showed a comprehensive effect across the entire GI tract, which can primarily be attributed to the great variability among replicates. Lower microbial diversity together with Ca supplementation have a negative influence in the growth performance of broilers. The sunbstantial community differences between digesta and mucosa derived samples indicate that both habitats have to be considered when the influence of diet on the gut microbiota, broiler growth performance and animal health is investigated.

研究背景：在肉鸡日粮中添加植酸酶（Phytase）是提升磷（Phosphorus, P）消化率、减少磷排泄流失的常规策略。提高磷的生物利用度并同步补充钙（Calcium, Ca），可对肉鸡消化道的微生物群落组成产生调控作用。本研究旨在厘清矿物磷、钙与植酸酶对肉鸡胃肠道（Gastrointestinal Tract, GIT）微生物群落组成的各自影响。

研究结果：各胃肠道区段的食糜与黏膜样本间均存在统计学差异。然而，对56只个体肉鸡的分析显示，同一日粮组的重复样本间微生物群落组成存在较高变异。所有日粮的食糜与黏膜样本重复组间的平均相似性，在嗉囊为29%~81%，回肠为18%~48%，盲肠为16%~38%。仅添加钙的日粮组肉鸡，其体增重、饲料转化率均为最低，微生物多样性也处于最低水平；而所有添加磷的日粮组均表现出最优的生长性能。本研究观察到不同日粮对嗉囊黏膜菌群存在显著影响，但食糜样本未呈现类似结果。回肠黏膜定植的微生物群落受磷添加的调控。与其他胃肠道区段相比，盲肠来源的样本微生物多样性最高。优势操作分类单元（Operational Taxonomic Unit, OTU）分属于粪杆菌属（Faecalibacterium）与假黄褐杆菌属（Pseudoflavonifractor），这两个属已知可影响肠道健康并为丁酸产生菌。

研究结论：不同日粮可对各胃肠道区段的微生物群落产生影响，但尚无任何日粮可对整个胃肠道产生全面调控作用，这一现象主要可归因于重复样本间的高度变异。钙添加与较低的微生物多样性共同对肉鸡的生长性能产生负面影响。食糜与黏膜来源样本间存在显著的群落差异，这表明在研究日粮对肠道菌群、肉鸡生长性能及动物健康的影响时，需同时考虑这两种微生境。