Ali Sikandar, Ni Xiaojun, Khan Muhammad, Zhao Xiaoqi, Yang Hongyuan, Danzeng Baiji, Raja Imtiaz Hussain, Quan Guobo
Yunnan Animal Science and Veterinary Institute, Jindian, Panlong District, Kunming 650225, China.
Zhejiang Vegamax Biotechnology Co., Ltd., Huzhou 313300, China.
Animals (Basel). 2023 Dec 29;14(1):121. doi: 10.3390/ani14010121.
Diet-associated characteristics such as dietary protein levels can modulate the gut's primary or secondary metabolites, leading to effects on the productive performance and overall health of animals. Whereas fecal metabolite changes are closely associated with gut metabolome, this study aimed to see changes in the rumen metabolite profile of lactating ewes fed different dietary protein levels. For this, eighteen lactating ewes (approximately 2 years old, averaging 38.52 ± 1.57 kg in their initial body weight) were divided into three groups ( = 6 ewes/group) by following the complete randomized design, and each group was assigned to one of three low-protein (D_I), medium-protein (D_m), and high-protein (D_h) diets containing 8.58%, 10.34%, and 13.93% crude protein contents on a dry basis, respectively. The fecal samples were subjected to untargeted metabolomics using ultra-performance liquid chromatography (UPLC). The metabolomes of the sheep fed to the high-protein-diet group were distinguished as per principal-component analysis from the medium- and low-protein diets. Fecal metabolite concentrations as well as their patterns were changed by feeding different dietary protein levels. The discriminating metabolites between groups of nursing sheep fed different protein levels were identified using partial least-squares discriminant analysis. The pathway enrichment revealed that dietary protein levels mainly influenced the metabolism-associated pathways ( = 63 and 39 in positive as well as negative ionic modes, respectively) followed by protein ( = 15 and 8 in positive as well as negative ionic modes, respectively) and amino-acid ( = 14 and 7 in positive as well as negative ionic modes, respectively) synthesis. Multivariate and univariate analyses showed comparative changes in the fecal concentrations of metabolites in both positive and negative ionic modes. Major changes were observed in protein metabolism, organic-acid biosynthesis, and fatty-acid oxidation. Pairwise analysis and PCA reveal a higher degree of aggregation within the D-h group than all other pairs. In both the PCA and PLS-DA plots, the comparative separation among the D_h/D_m, D_h/D_I, and D_m/D_I groups was superior in positive as well as negative ionic modes, which indicated that sheep fed higher protein levels had alterations in the levels of the metabolites. These metabolic findings provide insights into potentiated biomarker changes in the metabolism influenced by dietary protein levels. The target identification may further increase our knowledge of sheep gut metabolome, particularly regarding how dietary protein levels influence the molecular mechanisms of nutritional metabolism, growth performance, and milk synthesis of sheep.
饮食相关特征，如膳食蛋白质水平，可调节肠道的初级或次级代谢产物，从而影响动物的生产性能和整体健康。虽然粪便代谢产物的变化与肠道代谢组密切相关，但本研究旨在观察饲喂不同膳食蛋白质水平的泌乳母羊瘤胃代谢产物谱的变化。为此，采用完全随机设计将18只泌乳母羊（约2岁，初始体重平均为38.52±1.57 kg）分为三组（每组6只母羊），每组分别饲喂三种低蛋白（D_I）、中蛋白（D_m）和高蛋白（D_h）日粮之一，日粮干物质中粗蛋白含量分别为8.58%、10.34%和13.93%。粪便样本采用超高效液相色谱（UPLC）进行非靶向代谢组学分析。通过主成分分析，高蛋白日粮组绵羊的代谢组与中蛋白和低蛋白日粮组的代谢组有所区分。饲喂不同膳食蛋白质水平会改变粪便代谢产物浓度及其模式。使用偏最小二乘判别分析确定不同蛋白质水平的哺乳绵羊组之间的差异代谢产物。通路富集分析表明，膳食蛋白质水平主要影响与代谢相关的通路（分别在正离子和负离子模式下为63条和39条），其次是蛋白质（分别在正离子和负离子模式下为15条和8条）和氨基酸（分别在正离子和负离子模式下为14条和7条）合成。多变量和单变量分析显示，正离子和负离子模式下粪便代谢产物浓度均有比较性变化。观察到蛋白质代谢、有机酸生物合成和脂肪酸氧化有主要变化。成对分析和主成分分析显示，D-h组内的聚集程度高于所有其他组对。在主成分分析和偏最小二乘判别分析图中，D_h/D_m、D_h/D_I和D_m/D_I组在正离子和负离子模式下的比较分离均更明显，这表明饲喂较高蛋白质水平的绵羊代谢产物水平发生了变化。这些代谢研究结果为深入了解膳食蛋白质水平影响的代谢中潜在生物标志物变化提供了见解。靶点鉴定可能会进一步增加我们对绵羊肠道代谢组的了解，特别是关于膳食蛋白质水平如何影响绵羊营养代谢、生长性能和乳汁合成的分子机制。
