Wang Bing, Wang Diming, Wu Xuehui, Cai Jie, Liu Mei, Huang Xinbei, Wu Jiusheng, Liu Jianxin, Guan Leluo
Institute of Dairy Science, College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China.
MoE Key Laboratory of Molecular Animal Nutrition, Zhejiang University, Hangzhou, 310058, China.
BMC Genomics. 2017 May 6;18(1):353. doi: 10.1186/s12864-017-3726-2.
Rumen epithelial tissue plays an important role in nutrient absorption and rumen health. However, whether forage quality and particle size impact the rumen epithelial morphology is unclear. The current study was conducted to elucidate the effects of forage quality and forage particle size on rumen epithelial morphology and to identify potential underlying molecular mechanisms by analyzing the transcriptome of the rumen epithelium (RE). To achieve these objectives, 18 mid-lactation dairy cows were allocated to three groups (6 cows per group), and were fed with one of three different forage-based diets, alfalfa hay (AH), corn stover (CS), and rice straw (RS) for 14 weeks, respectively. Ruminal volatile fatty acids (VFAs) and epithelial thickness were determined, and RNA-sequencing was conducted to identify the transcriptomic changes of rumen epithelial under different forage-based diets.
The RS diet exhibited greater particle size but low quality, the AH diet was high nutritional value but small particle size, and CS diet was low quality and small particle size. The ruminal total VFA concentration was greater in AH compared with those in CS or RS. The width of the rumen papillae was greater in RS-fed cows than in cows fed AH or CS. In total, 31, 40, and 28 differentially expressed (DE, fold change > 2, FDR < 0.05) genes were identified via pair-wise comparisons including AH vs. CS, AH vs. RS, and RS vs. CS, respectively. Functional classification analysis of DE genes revealed dynamic changes in ion binding (such as DSG1) between AH and CS, proliferation and apoptotic processes (such as BAG3, HLA-DQA1, and UGT2B17) and complement activation (such as C7) between AH or RS and CS. The expression of HLA-DQA1 was down-regulated in RS compared with AH and CS, and the expression of UGT2B17 was down-regulated in RS compared with CS, with positive (R = 0.94) and negative (R = -0.96) correlation with the width of rumen epithelial papillae (P < 0.05), respectively.
Our results suggest that both nutrients (VFAs) and particle sizes can alter expression of genes involved in cell proliferation/apoptosis process and complement complex. Our results suggest that particle size may be more important in regulating rumen epithelial morphology when animals are fed with low-quality forage diets and the identified DE genes may affect the RE nutrient absorption or morphology of RE. Our findings provide insights into the effects of the dietary particle size in the future management of dairy cow feeding, that when cows were fed with low-quality forage (such as rice straw), smaller particle size may be beneficial for nutrients absorption and milk production.
瘤胃上皮组织在营养物质吸收和瘤胃健康方面发挥着重要作用。然而，饲料质量和颗粒大小是否会影响瘤胃上皮形态尚不清楚。本研究旨在阐明饲料质量和饲料颗粒大小对瘤胃上皮形态的影响，并通过分析瘤胃上皮（RE）的转录组来确定潜在的分子机制。为实现这些目标，将18头处于泌乳中期的奶牛分为三组（每组6头），分别用三种不同的以草料为基础的日粮苜蓿干草（AH）、玉米秸秆（CS）和稻草（RS）喂养14周。测定瘤胃挥发性脂肪酸（VFA）和上皮厚度，并进行RNA测序以确定不同草料日粮下瘤胃上皮的转录组变化。
RS日粮颗粒尺寸较大但质量较低，AH日粮营养价值高但颗粒尺寸较小，CS日粮质量低且颗粒尺寸较小。与CS或RS相比，AH组瘤胃总VFA浓度更高。饲喂RS的奶牛瘤胃乳头宽度大于饲喂AH或CS的奶牛。通过成对比较，包括AH与CS、AH与RS、RS与CS，分别鉴定出31、40和28个差异表达（DE，倍数变化>2，FDR<0.05）基因。对DE基因的功能分类分析揭示了AH与CS之间离子结合（如DSG1）、AH或RS与CS之间增殖和凋亡过程（如BAG3、HLA-DQA1和UGT2B17）以及补体激活（如C7）的动态变化。与AH和CS相比，RS中HLA-DQA1的表达下调，与CS相比，RS中UGT2B17的表达下调，分别与瘤胃上皮乳头宽度呈正相关（R=0.94）和负相关（R=-0.96）（P<0.05）。
我们的结果表明，营养物质（VFA）和颗粒大小均可改变参与细胞增殖/凋亡过程和补体复合物的基因表达。我们的结果表明，当动物饲喂低质量草料日粮时，颗粒大小在调节瘤胃上皮形态方面可能更重要，并且鉴定出的DE基因可能影响RE的营养吸收或RE的形态。我们的研究结果为日粮颗粒大小在奶牛饲养未来管理中的作用提供了见解，即当奶牛饲喂低质量草料（如稻草）时，较小的颗粒大小可能有利于营养吸收和产奶。
