1 research outputs found
Correlations between Milk and Plasma Levels of Amino and Carboxylic Acids in Dairy Cows
The
objective of this study was to investigate the relationship between
the concentrations of 19 amino acids, glucose, and seven carboxylic
acids in the blood and milk of dairy cows and their correlations with
established markers of ketosis. To that end, blood plasma and milk
specimens were collected throughout lactation in two breeds of dairy
cows of different milk yield. Plasma concentrations of glucose, pyruvate,
lactate, α-aminobutyrate, β-hydroxybutyrate (BHBA), and
most amino acids, except for glutamate and aspartate, were on average
9.9-fold higher than their respective milk levels. In contrast, glutamate,
aspartate, and the Krebs cycle intermediates succinate, fumarate,
malate, and citrate were on average 9.1-fold higher in milk than in
plasma. For most metabolites, with the exception of BHBA and threonine,
no significant correlations were observed between their levels in
plasma and milk. Additionally, milk levels of acetone showed significant
direct relationships with the glycine-to-alanine ratio and the BHBA
concentration in plasma. The marked decline in plasma concentrations
of glucose, pyruvate, lactate, and alanine in cows with plasma BHBA
levels above the diagnostic cutoff point for subclinical ketosis suggests
that these animals fail to meet their glucose demand and, as a consequence,
rely increasingly on ketone bodies as a source of energy. The concomitant
increase in plasma glycine may reflect not only the excessive depletion
of protein reserves but also a potential deficiency of vitamin B<sub>6</sub>