摘要
Feed efficient cattle consume less feed and produce less environmental waste than inefficient cattle. Many factors are known to contribute to differences in feed efficiency. However, it is unknown how the rumen epithelium and its associated microorganisms influence the feed efficiency of cattle. Our study aimed to understand how host gene expression in the rumen epithelium and the activity of rumen epithelial attached microbes contribute to differences in feed efficiency. Residual feed intake (RFI) of 175 Hereford x Angus steers was measured using a GrowSafe system. The rumen epithelial transcriptome from 9 of the most efficient (low (L-) RFI) and 9 of the most inefficient (high (H-) RFI) steers was obtained using RNA-seq. Differential gene expression analysis was conducted using DESeq2 software and Weighted Gene Co-expression Network Analysis (WGCNA) was performed to identify gene modules that are correlated with RFI. Additionally, we identified and quantified the relative abundance of bacterial and archaeal 16S rRNA transcripts as an indication of their activity. Within the rumen epithelium there were 122 genes that were differentially expressed between L- and H- RFI steers (p<0.05). Also, WGCNA identified a significant module of 764 genes that negatively correlated with RFI (r=-0.5, p=0.03). Functional analysis revealed up-regulation of genes in the L-RFI epithelium involved in modulation of intercellular adhesion, cell migration, cytoskeletal organization, protein and cell turnover, oxidative phosphorylation, and acetylation. Our results suggest the increased tissue morphogenesis in the L-RFI epithelium may increase epithelial paracellular permeability for the absorption of nutrients. Up-regulation of oxidative phosphorylation and acetylation in the L-RFI epithelium indicate potential increased energy production to support the energetic demands of increased tissue morphogenesis in feed efficient animals. There was no significant difference between RFI groups in the activity of archaeal phylotypes on the epithelium. However, the bacterial families Campylobacteraceae and Neisseriaceae had significantly greater activity on the L-RFI epithelium (p<0.05) and they play a role in oxygen scavenging. Overall, L-RFI (efficient) steers may have increased rumen tissue morphogenesis that possibly increase paracellular permeability for the absorption of nutrients, thereby providing a greater substrate supply for whole-body energy production. They also have greater activity of rumen epithelial attached oxygen scavenging bacteria that may provide more optimal feed fermentation conditions, which contributes to high feed efficiency.
摘要译文
饲料有效的牛消耗的饲料较少，而产生的环境废物比效率低下的牛会更少。已知许多因素有助于饲料效率的差异。但是，尚不清楚瘤胃上皮及其相关的微生物如何影响牛的饲料效率。我们的研究旨在了解瘤胃上皮中的宿主基因表达如何以及瘤胃上皮附着的微生物的活性有助于饲料效率的差异。使用GROWSAFE系统测量了175 Hereford X Angus Steers的残留饲料摄入量（RFI）。使用RNA-seq获得了9个最有效（低（L-）RFI）和最低效率（高（H-）RFI）的9个瘤胃上皮转录组。使用DESEQ2软件进行了差异基因表达分析，并进行了加权基因共表达网络分析（WGCNA），以识别与RFI相关的基因模块。此外，我们确定并量化了细菌和古细菌16S rRNA转录本的相对丰度，以表明其活性。在瘤胃上皮中，有122个基因在L-和H-RFI转向器之间差异表达（P <0.05）。同样，WGCNA确定了一个与RFI负相关的764个基因的显着模块（r = -0.5，p = 0.03）。功能分析表明，L-RFI上皮的基因上调参与了细胞间粘附，细胞迁移，细胞骨架组织，蛋白质和细胞周转，氧化磷酸化和乙酰化的调节。我们的结果表明，L-RFI上皮的组织形态发生增加可能会增加上皮细胞细胞的渗透性，以吸收养分。 L-RFI上皮中氧化磷酸化和乙酰化的上调表明潜在的能量产生增加，以支持有效动物中组织形态发生增加的能量需求。 RFI组在古细胞型在上皮上的活性中没有显着差异。然而，细菌家族弯曲杆菌科和奈瑟氏菌科在L-RFI上皮的活性明显更大（P <0.05），它们在氧气清除中起着作用。总体而言，L-RFI（有效）转转可能会增加瘤胃组织形态发生，从而增加细胞细胞的渗透性以吸收营养素，从而为全身能量产生提供更大的基板供应。它们还具有更大的瘤胃上皮附着的氧气清除细菌的活性，该细菌可能提供更佳的饲料发酵条件，从而有助于高饲料效率。
Kong, Rebecca. Contribution of the Rumen Epithelial Transcriptome and Microbial Community to Variation in Beef Cattle Feed Efficiency[D]. CA: University of Alberta, 2016