The Study of Yak Colostrum Nutritional Content Based on Foodomics

Abstract

The utilization of yak milk is still in a primary stage, and the nutrition composition of yak colostrum is not systematically characterized at present. In this study, the lipids, fatty acids, amino acids and their derivatives, metabolites in yak colostrum, and mature milk were detected by the non-targeted lipidomics based on (ultra high performance liquid chromatography tandem quadrupole mass spectrometer) UHPLC-MS, the targeted metabolome based on gas chromatography-mass spectrometer (GC-MS), the targeted metabolome analysis based on UHPLC-MS, and the non-targeted metabolome based on ultra high performance liquid chromatography tandem quadrupole time of flight mass spectrometer (UHPLC-TOF-MS), respectively. Meanwhile, the nutrition composition of yak colostrum was compared with the data of cow mature milk in the literatures. The results showed that the nutritive value of yak colostrum was higher by contrast with yak and cow mature milk from the perspective of the fatty acid composition and the content of Σpolyunsaturated fatty acids (PUFAs), Σn-3PUFAs; the content of essential amino acid (EAA) and the ratio of EAA/total amino acid (TAA) in yak colostrum were higher than the value in yak mature milk; and the content of functional active lipids including phosphatidylcholines (PC), phosphatidylglycerol (PG), phosphatidylserine (PS), lyso-phosphatidylcholine (LPC), lyso-phosphatidylglycerol (LPG), lyso-phosphatidylinositol (LPI), sphingomyelin (SM), ganglioside M3 (GM3), ganglioside T3 (GT3), and hexaglycosylceramide (Hex1Cer) in yak colostrum, was higher than the value of yak mature milk. Moreover, the differences of nutritive value between yak colostrum and mature milk were generated by the fat, amino acids and carbohydrate metabolism that were regulated by the ovarian hormone and referencesrenin-angiotensin-aldosterone system in yaks. These research results can provide a theoretical basis for the commercial product development of yak colostrum.

Keywords: colostrum; foodomics; functional ingredient; regulatory mechanism; yak.

Figure 1

(a) Bar chart of the lipid subclasses and molecule numbers in yak milk. The abscissa represents the detected lipid subclass, and the ordinate represents the number of lipid molecules. (b) Composition of lipid subclasses in yak colostrum. C: colostrum. Different lipid subclasses are represented by the different colors, and the proportion is represented by the area size. (c) Composition of the lipid subclasses in yak mature milk. M: mature milk.

Figure 2

(a) The score plots of the principal component analysis (PCA) of lipids in yak colostrum, mature milk, and quality control (QC) samples. Green, blue, and red represent the samples of yak colostrum, mature milk, and QC, respectively. (b) The score plots of the orthogonal partial least squares discriminant analysis (OPLS−DA) of lipids in yak colostrum and mature milk. Green and blue represent the samples of yak colostrum and mature milk, respectively. (c) Permutation test of OPLS−DA model.

Figure 3

(a) Volcano plot of the lipids abundance in yak colostrum by contrast with mature milk. The abscissa represent the value of log₂ fold change (FC), and the ordinate represent the value of −log₁₀ p. A point represents a lipid molecule. The points with FC > 1.5 or < 0.67, p < 0.05 are shown with red, and non-significantly different lipids (SDLs) are shown with black. (b) Cluster heat map of SDLs. Each row represents a SDL, and each column represents a samples. The color blocks at different positions represent the abundance of lipid molecules. Red represented a high abundance, and blue represented a low abundance. (c) Chord diagram of lipid subclasses. The starting point of link in the inner circle represented the SDL, and the arc on the outer circle represents the lipid subclasses. The colored lines indicate the correlations of lipid molecules within the subclass, and the lines are the same color as the subclass. The dark gray lines indicate the correlations between the subclasses.

Figure 4

(a) PCA score plots of the metabolites in yak colostrum milk, mature milk, QC in positive ionization mode. Green, blue, and red represent the samples of yak colostrum milk, mature milk, QC, respectively. (b) PCA score plots of the metabolites in the yak colostrum milk, mature milk, QC in negative ionization mode. (c) OPLS−DA score plots of the metabolites in the yak colostrum and mature milk in positive ionization mode. Green and blue represent the samples of yak colostrum milk and mature milk, respectively. (d) OPLS−DA score plots of the metabolites in the yak colostrum and mature milk in negative ionization mode. (e) Permutation test of OPLS−DA in positive ionization mode. (f) Permutation test of OPLS−DA in negative ionization mode.

Figure 5

The number proportion of the identified metabolites in each chemical classification.

Figure 6

(a) Volcano plot of the metabolites abundance in yak colostrum by contrast with mature milk in positive ionization mode. The abscissa represents the value of log₂ FC, and the ordinate represents the value of −log₁₀ p. A point represents a metabolites molecule. The points with FC > 1.5 and p < 0.05 are shown with red; the points with FC < 0.67 and p < 0.05 are shown with blue; non-differential metabolites (DMs) are shown with black. (b) Volcano plot of the metabolites abundance in yak colostrum by contrast with mature milk in negative ionization mode. (c) Correlation heat map of the top 20 DMs in positive ionization mode. Red indicates the positive correlation; blue indicates the negative correlation; white indicates the non-significant correlation. The color depth was related to the absolute value of correlation coefficient. The higher the positive or negative correlation was, the darker the color was. The dot size was related to the correlation significance. The more significant the correlation was, the larger the dot was. (d) Correlation heat map of the top 20 DMs in negative ionization mode.

Figure 7

Differential abundance (DA) scores of all the enriched KEGG pathways. The Y-axis represented the name of metabolic pathway, and the X-axis represented the DA score. The DA score 1 indicated the up-regulated trend of all identified metabolites in this pathway, and −1 indicated the down-regulated trend of all identified metabolites in this pathway. The length of the line segment represented the absolute value of the DA score, and the size of the dot at the end of the line segment represented the number of metabolites in the pathway. The dot color was proportional to the DA score.