Correlations between Milk and Plasma Levels of Amino and Carboxylic Acids in Dairy Cows

Abstract

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-toalanine 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 6 .

Tryptophan, kynurenine, kynurenic acid concentrations and indoleamine 2,3‐dioxygenase activity in serum and milk of dairy cows with subclinical mastitis caused by coagulase‐negative staphylococci

“…Previous studies indicate that serum TRP can be affected by the animal feed, the lactation phase and even the breed of cows. Klein et al (2013) reported (Klein et al, 2013). In our study, the level of TRP in serum of healthy cows was 39.29 μM and was similar to that reported by other authors (Klein et al, 2013;Kollmann et al, 2008;Laeger, Görs, Metges, & Kuhla, 2012).…”

“…In Brown Swiss cows in the early lactation stage, serum TRP content was 37.3 μmol/L; however, in the subsequent lactation period, it was higher by 25%. Also in Simmental cows, a difference of 18.8% in serum TRP levels between late and early stage of lactation (37.5 and 31.6 μmol/L, respectively) was reported (Klein et al, ). In our study, the level of TRP in serum of healthy cows was 39.29 μM and was similar to that reported by other authors (Klein et al, ; Kollmann et al, ; Laeger, Görs, Metges, & Kuhla, ).…”

“…We found that the level of TRP in the milk of these cows was significantly lower than in their serum. Similarly, Klein et al (2013) showed that TRP levels are lower in milk than in serum regardless of breed of cows and stage of lactation. Authors claim that the marked differences in plasma and milk concentrations of TRP as well as other amino acids reflect their widespread use by the mammary gland for milk protein synthesis and generation of gluconeogenic and ketogenic precursors (Klein et al, 2013).…”

“…Previous studies indicate that serum TRP can be affected by the animal feed, the lactation phase and even the breed of cows. Klein et al () investigated the levels of amino acids in milk and serum of Brown Swiss and Simmental cows in different phases of lactation. In Brown Swiss cows in the early lactation stage, serum TRP content was 37.3 μmol/L; however, in the subsequent lactation period, it was higher by 25%.…”

Identification of disordered metabolic networks in postpartum dairy cows with left displacement of the abomasum through integrated metabolomics and pathway analyses

“…Vitamin B 6 , as a co-factor for more than 150 enzymes, has multiple biological activities in the regulation of the metabolism and synthesis of carbohydrates, lipids and proteins [25]. In addition to its coenzyme role, this vitamin was recognized as an antioxidant and anti-inflammatory agent in recent years [4].…”