The influence of bovine diet on the metabolome of reconstituted skim milk powder (SMP) and protein ingredients produced from the milk of cows fed on pasture or concentrate-based diets was investigated. Cows were randomly assigned to diets consisting of perennial ryegrass only (GRS), perennial ryegrass/white clover sward (CLV), or indoor total mixed ration (TMR) for an entire lactation. Raw milk obtained from each group was processed at pilot scale, to produce SMP and sweet whey, and SMP was further processed at laboratory scale, to yield ideal whey and acid whey. The total amino acid composition and metabolome of each sample were analyzed, using high-performance cation exchange and a targeted combination of direct-injection mass spectrometry and reverse-phase liquid chromatography-tandem mass spectrometry (LC-MS/MS), respectively. The nitrogen composition of the products from each of the diets was similar, with one exception being the significantly higher nonprotein nitrogen content in TMR-derived skim milk powder than that from the GRS system. Total amino acid analysis showed significantly higher concentrations of glycine in GRS- and CLV-derived sweet whey and acid whey than in those from TMR. The cysteine contents of CLV-derived ideal whey and acid whey were significantly higher than for TMR, while the valine content of GRS-derived acid whey was significantly higher than TMR. The phenylalanine content of GRS-derived ideal whey was significantly higher than that from CLV. Metabolomic analysis showed significantly higher concentrations of the metabolites glutamine, valine, and phosphocreatine in each ingredient type derived from TMR than those from GRS or CLV, while the serine content of each GRS-derived ingredient type was significantly higher than that in TMR-derived ingredients. These results demonstrate that the type of bovine feeding system used can have a significant effect on the amino acid composition and metabolome of skim milk and whey powders and may aid in the selection of raw materials for product manufacture, while the clear separation between the samples gives further evidence for distinguishing milk products produced from different feeding systems based on LC-MS/MS.

中文翻译：

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牛饮食对脱脂牛奶和乳清蛋白成分代谢组学特性的影响。

研究了牛饮食对重构脱脂奶粉（SMP）代谢组的影响以及由以牧场或浓缩饲料为基础饲喂的母牛的牛奶中产生的蛋白质成分的影响。在整个泌乳期间，将母牛随机分配为仅由多年生黑麦草（GRS），多年生黑麦草/白三叶草（CLV）或室内总混合日粮（TMR）组成的日粮。从每组中获得的原料奶以中试规模加工，以生产SMP和甜乳清，SMP在实验室规模中进一步加工，以生产理想的乳清和酸乳清。使用高效阳离子交换以及直接进样质谱和反相液相色谱-串联质谱（LC-MS / MS）的目标组合分别分析了每个样品的总氨基酸组成和代谢组学。每种饮食中产品的氮成分相似，唯一的例外是，TMR来源的脱脂奶粉中的非蛋白质氮含量明显高于GRS系统中的非蛋白质氮含量。总氨基酸分析显示，在GRS和CLV衍生的甜乳清和酸乳清中，甘氨酸的浓度显着高于TMR。CLV衍生的理想乳清和酸乳清的半胱氨酸含量显着高于TMR，而GRS衍生的酸乳清的缬氨酸含量显着高于TMR。GRS衍生的理想乳清的苯丙氨酸含量显着高于CLV。代谢组学分析显示，TMR衍生的每种成分类型中的代谢产物谷氨酰胺，缬氨酸和磷酸肌酸的浓度均显着高于GRS或CLV，而每种GRS衍生成分的丝氨酸含量均显着高于TMR衍生成分。这些结果表明，所用的牛饲喂系统类型可以对脱脂奶和乳清粉的氨基酸组成和代谢组产生重大影响，并且可以帮助选择产品制造原料，而样品之间的清晰分离可以基于LC-MS / MS区分不同喂养系统生产的乳制品的进一步证据。