Yang Zhuqing, Chen Xiao, Yu Mingjin, Jing Ruixue, Bao Linbin, Zhao Xianghui, Pan Ke, Chao Bihui, Qu Mingren
College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang, China.
Jiangxi Provincial Key Laboratory for Animal Nutrition/Engineering Research Center of Feed Development, Jiangxi Agricultural University, Nanchang, China.
Front Microbiol. 2024 Mar 11;15:1334068. doi: 10.3389/fmicb.2024.1334068. eCollection 2024.
Niacin is one of the essential vitamins for mammals. It plays important roles in maintaining rumen microecological homeostasis. Our previous study indicated that dietary niacin significantly elevated intramuscular fat content (IMF) in castrated finishing steers. Whether niacin affects fat deposition by regulating the microbial composition and functional capacities of gastrointestinal microbiome has been unknown yet.
In this study, 16 castrated Xiangzhong Black cattle were randomly assigned into either control group fed with a basal concentrate diet ( = 8) or niacin group fed with a basal concentrate diet added 1000 mg/kg niacin ( = 8). Seven rumen samples and five cecum content samples were randomly collected from each of control and niacin groups for metagenomic sequencing analysis.
A total of 2,981,786 non-redundant microbial genes were obtained from all tested samples. Based on this, the phylogenetic compositions of the rumen and cecum microbiome were characterized. We found that bacteria dominated the rumen and cecum microbiome. and were the most abundant bacterial species in the rumen microbiome, while and were predominant bacterial species in the cecum microbiome. Rumen microbiome had significantly higher abundances of GHs, GTs, and PLs, while cecum microbiome was enriched by CBMs and AAs. We found a significant effect of dietary niacin on rumen microbiome, but not on cecum microbiome. Dietary niacin up-regulated the abundances of bacterial species producing lactic acid and butyrate, fermenting lactic acid, and participating in lipid hydrolysis, and degradation and assimilation of nitrogen-containing compounds, but down-regulated the abundances of several pathogens and bacterial species involved in the metabolism of proteins and peptides, and methane emissions. From the correlation analysis, we suggested that niacin improved nutrient digestion and absorption, but reduced energy loss, and Valine, leucine and isoleucine degradation of rumen microbiome, which resulted in the increased host IMF.
The results suggested that dietary manipulation, such as the supplementation of niacin, should be regarded as the effective and convenient way to improve IMF of castrated finishing steers by regulating rumen microbiome.
烟酸是哺乳动物必需的维生素之一。它在维持瘤胃微生态平衡中发挥着重要作用。我们之前的研究表明，日粮烟酸能显著提高去势育肥牛的肌内脂肪含量（IMF）。然而，烟酸是否通过调节胃肠道微生物群的组成和功能来影响脂肪沉积尚不清楚。
本研究将16头去势湘中黑牛随机分为两组，对照组饲喂基础精料日粮（n = 8），烟酸组饲喂添加1000 mg/kg烟酸的基础精料日粮（n = 8）。从对照组和烟酸组中每组随机采集7份瘤胃样本和5份盲肠内容物样本进行宏基因组测序分析。
从所有测试样本中总共获得了2,981,786个非冗余微生物基因。基于此，对瘤胃和盲肠微生物群的系统发育组成进行了表征。我们发现细菌在瘤胃和盲肠微生物群中占主导地位。普雷沃氏菌属和丁酸弧菌属是瘤胃微生物群中最丰富的细菌种类，而拟杆菌属和瘤胃球菌属是盲肠微生物群中的优势细菌种类。瘤胃微生物群中糖苷水解酶（GHs）、糖基转移酶（GTs）和多糖裂解酶（PLs）的丰度显著更高，而盲肠微生物群中则富含碳水化合物结合模块（CBMs）和辅助活性（AAs）。我们发现日粮烟酸对瘤胃微生物群有显著影响，但对盲肠微生物群没有影响。日粮烟酸上调了产生乳酸和丁酸、发酵乳酸以及参与脂质水解和含氮化合物降解与同化的细菌种类的丰度，但下调了几种病原体以及参与蛋白质和肽代谢及甲烷排放的细菌种类的丰度。通过相关性分析，我们认为烟酸改善了营养物质的消化吸收，但减少了能量损失，以及瘤胃微生物群中缬氨酸、亮氨酸和异亮氨酸的降解，这导致宿主肌内脂肪含量增加。
结果表明，日粮调控，如添加烟酸，应被视为通过调节瘤胃微生物群来提高去势育肥牛肌内脂肪含量的有效且便捷的方法。
