Abstract：
Heat stress (HS) is a critical challenge in broilers due to the high metabolic rate and lack of sweat glands. Results from this study show that implementing a cyclic chronic HS (34 °C for 7 h/d) to finisher broilers decreased the diversity of cecal microbiota and impaired intestinal barrier, resulting in gut leak and decreased body weight (both P < 0.05). These alterations might be related to inflammatory outbursts and the retarded proliferation of intestinal epithelial cells (IECs) according to the transcriptome analysis. Considering the potential beneficial properties of Lactobacillus on intestinal development and function, the protective effects of Lactobacillus rhamnosus (L. rhamnosus) on the intestine were investigated under HS conditions in this study. Orally supplemented L. rhamnosus improved the composition of cecal microbiota and upregulated the transcription of tight junction proteins in both duodenum and jejunum, with a consequent suppression in intestinal gene expressions of pro-inflammatory cytokines and facilitation in digestive capability. Meanwhile, the jejunal villus height of the birds that received L. rhamnosus was significantly higher compared with those treated with the broth (P < 0.05). The expression abundances of genes related to IECs proliferation and differentiation were increased by L. rhamnosus, along with upregulated mRNA levels of Wnt3a and β-catenin in jejunum. In addition, L. rhamnosus attenuated enterocyte apoptosis as indicated by decreased caspase-3 and caspase-9 gene expressions. The results indicated that oral administration with L. rhamnosus mitigated HS-induced dysfunction by promoting intestinal development and epithelial maturation in broilers and that the effects of L. rhamnosus might be dependent of Wnt/β-catenin signaling.
摘要：
由于高代谢率和缺乏汗腺，热应激（HS）是肉鸡面临的关键挑战。这项研究的结果表明，实施循环慢性HS（34°C，7小时/天）的完成肉鸡减少盲肠微生物群的多样性和受损的肠屏障，导致肠道渗漏和体重下降（均P<0.05）。根据转录组分析，这些改变可能与炎症爆发和肠上皮细胞（IECs）的延迟增殖有关。考虑到乳酸菌对肠道发育和功能的潜在有益特性，鼠李糖乳杆菌（L.鼠李糖）在本研究中在HS条件下研究了肠道。口腔补充鼠李糖乳杆菌改善了盲肠微生物群的组成，并上调了十二指肠和空肠中紧密连接蛋白的转录，从而抑制肠道促炎细胞因子的基因表达并促进消化能力。同时,与肉汤处理的鸟类相比，接受鼠李糖乳杆菌的空肠绒毛高度显着升高（P<0.05）。鼠李糖乳杆菌增加了与IECs增殖和分化相关的基因的表达丰度，空肠中Wnt3a和β-catenin的mRNA水平上调。此外,鼠李糖乳杆菌减弱肠细胞凋亡，caspase-3和caspase-9基因表达降低。结果表明，口服鼠李糖乳杆菌通过促进肉鸡肠道发育和上皮成熟来减轻HS诱导的功能障碍，鼠李糖乳杆菌的作用可能依赖于Wnt/β-catenin信号传导。
