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Impact of Bovine Diet on Metabolomic Profile of Skim Milk and Whey Protein Ingredients
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2019-12-17
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Magan, J.B.; O’Callaghan, T.F.; Zheng, J.; Zhang, L.; Mandal, R.; Hennessy, D.; Fenelon, M.A.; Wishart, D.S.; Kelly, A.L.; McCarthy, N.A. Impact of Bovine Diet on Metabolomic Profile of Skim Milk and Whey Protein Ingredients. Metabolites 2019, 9, 305. https://doi.org/10.3390/metabo9120305
Abstract
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