Increase dietary fiber intake ameliorated cecal morphology and drove cecal species-specific of short-chain fatty acids in White Pekin ducks

The current study was to investigate the effects of total dietary fiber (TDF) levels on modulating cecal morphology and the response of microbiota to maintain gut health for duck growth. A total of 192 male White Pekin ducks of 14-days-old were randomly allocated and fed diets containing 12.4%, 14.7% and 16.2% TDF until 35 days under the quantitative feed intake. Each dietary group consisted eight replicates with eight birds each. The results revealed that 14.7% and 16.2% TDF groups significantly promoted growth performance and improved villus height, ratio of villus to crypt, muscle layer thickness and goblet cells per villus of cecum in ducks. qPCR results showed that the transcriptional expression of Claudin-1, Muc2, IGF-1 and SLC16A1 were significantly up-regulated in cecum in 14.7% and 16.2% TDF groups. Meanwhile, the concentrations of IGF-1 and DAO in circulating were significantly increased in 14.7% and 16.2% TDF groups. Furthermore, the concentrations of butyrate, isobutyrate, valerate and isovalerate in cecum were conspicuously improved in 14.7% and 16.2% TDF group while that of propionate was significantly decreased. In addition, the concentration of butyrate, isobutyrate, valerate and isovalerate in cecum presented negative correlations with the concentration of DAO in circulating. 16S rRNA gene sequencing results showed that 14.7% TDF group importantly elevated the microbial richness. Simultaneously, butyrate-producing bacteria like the family Lachnospiraceae, Oscillospiraceae and Erysipelatoclostridiaceae were enriched as biomarkers in 16.2% TDF group. Correlation network analysis revealed that the associations between specific bacteria and short-chain fatty acids (SCFAs) induced by different TDF levels, and the correlations with bacteria. For example, the genus Monoglobus and CHKCI002 showed a positive correlation with butyrate and there was a positively coexistent association between Monoglobus and CHKCI002. In summary, these data revealed that increasing TDF level could enhance the cecal morphology and drive cecal species-specific of SCFAs in ducks.

本研究旨在探究日粮总膳食纤维（total dietary fiber, TDF）水平对肉鸭生长过程中盲肠形态调控、微生物群响应及维持肠道健康的影响。选取192只14日龄雄性北京白鸭，随机分组后在定量饲喂条件下，分别饲喂总膳食纤维含量为12.4%、14.7%及16.2%的日粮，饲养至35日龄。每个日粮组设置8个重复单元，每个单元包含8只试验鸭。试验结果显示，14.7%与16.2% TDF组可显著提升肉鸭生长性能，并改善盲肠绒毛高度、绒隐比、肌层厚度及每个绒毛的杯状细胞数目。实时荧光定量PCR（quantitative PCR, qPCR）结果表明，14.7%与16.2% TDF组鸭盲肠组织中Claudin-1、Muc2、IGF-1及SLC16A1的转录表达水平显著上调。与此同时，两组试验鸭循环血液中IGF-1与DAO的浓度均显著升高。此外，14.7%与16.2% TDF组鸭盲肠内容物中的丁酸、异丁酸、戊酸及异戊酸浓度显著提升，而丙酸浓度则显著降低。进一步分析发现，盲肠中丁酸、异丁酸、戊酸及异戊酸的浓度与循环血液中DAO的浓度呈显著负相关。16S rRNA基因测序结果显示，14.7% TDF组可显著提升肠道微生物群落的丰富度。同时，16.2% TDF组中以毛螺菌科（Lachnospiraceae）、颤螺菌科（Oscillospiraceae）及厄氏梭菌科（Erysipelatoclostridiaceae）为代表的产丁酸菌作为生物标志物显著富集。相关性网络分析揭示了不同TDF水平诱导的特定肠道细菌与短链脂肪酸（short-chain fatty acids, SCFAs）之间的关联模式，以及细菌类群间的相互关系：例如，Monoglobus属与CHKCI002菌属均与丁酸浓度呈正相关，且二者之间存在正向共存关联。综上，本研究数据表明，提升日粮总膳食纤维水平可改善肉鸭盲肠形态，并驱动盲肠产生特异性短链脂肪酸。