荷斯坦奶牛初乳与常乳代谢物差异分析

Differences in metabolites of colostrum and mature milk of Holstein cows

【目的】基于非靶向代谢组学技术,对荷斯坦奶牛初乳和常乳中的代谢物进行鉴定与分析。【方法】选择年龄、体况及预产期相近、胎次相同的健康围产期经产荷斯坦奶牛12头,分别于分娩后1 h和21 d采集乳汁,离心并收集乳清,依次记为初乳组(C_0)和常乳组(C_21)。采用代谢组学技术对初乳组和常乳组乳清进行分析,结合正交偏最小二乘判别分析(OPLS-DA)和学生t检验,以变量投影重要度(variable importance in the projection,VIP)>1,P<0.05为标准筛选差异代谢物,并对筛选出的差异代谢物进行聚类分析、显著差异代谢物筛选和KEGG通路分析。【结果】在荷斯坦奶牛初乳组(C_0)和常乳组(C_21)共筛选到97种差异代谢物,通过聚类热图可以看出,大多数代谢物在初乳组的含量高于常乳组;差异代谢物随机森林图显示,排名靠前的9种显著差异代谢物分别为乌头酸、柠康酸、龙胆酸、泛酸、牛磺酸、氧戊二酸、柠檬酸、6’唾液酸乳糖和精胺。KEGG通路富集分析显示,8条主要的代谢通路分别为酮体的合成与降解、牛磺酸与次黄嘌呤代谢、丙酮酸代谢、嘌呤代谢、嘧啶代谢、氨基糖与核苷酸糖代谢、三羧酸循环和丁酸代谢。【结论】荷斯坦奶牛初乳中脂质、氨基酸和核苷酸代谢物的含量高于常乳,而常乳中糖类代谢物含量高于初乳,初乳与常乳中代谢物水平的差异为后续代谢物机制的研究奠定了理论基础。

【Objective】Based on non-targeted metabolomics approach,the metabolites in colostrum and mature milk of Holstein cows were identified and analyzed.【Method】Twelve healthy perinatal Holstein cows with similar age,body condition,expected delivery date and parity were selected and milk was collec-ted at 1 h and 21 d after delivery.Then,milk was centrifuged and whey proteins were collected and marked as colostrum group(C_0)and mature milk group(C_21).Metabonomics technology was used to analyze whey of colostrum group and mature milk group.Combined with orthogonal partial least squares discriminant analysis(OPLS-DA)and student t test,differential metabolites were screened based on variable importance in projection(VIP)>1 with significant differences(P<0.05),and then cluster analysis,signi-ficant difference metabolite screening and KEGG pathway analysis were performed.【Result】A total of 97 differential metabolites were screened from colostrum group(C_0)and mature milk group(C_21)of Holstein cows.The contents of most metabolites in colostrum group were higher than that in mature milk group.The differential metabolite random forest map showed that the top nine metabolites with significant difference were aconitic acid,limoconic acid,gentian acid,pantothenic acid,taurine,oxyglutaric acid,citric acid,6’sialic lactose and spermine.The KEGG pathway enrichment analysis showed that the 8 major metabolic pathways were synthesis and degradation of ketones,taurine and hypoxanthine metabolism,pyruvate metabolism,purine metabolism,pyrimidine metabolism,amino sugar and nucleotide sugar metabolism,tricarboxylic acid cycle and butyric acid metabolism.【Conclusion】The contents of lipid,amino acid and nucleotide metabolites in colostrum of Holstein cows were higher than those in mature milk,while the contents of carbohydrate metabolites in mature milk were higher than those in colostrum.The differences in metabolite levels between colostrum and mature milk obtained in this study provided a basis for subsequent research on metabolite mechanisms.