Abstract
BackgroundBlood profiles have been used to monitor herd health status, diagnose disorders, and predict the risk of diseases in cattle and calves. Characterizing plasma metabolites in dairy calves could provide further insight into daily metabolic variations and the mechanisms that lead to metabolic diseases. In addition, by understanding physiological ranges of plasma metabolites relative to meal and the time of feeding in healthy animals, veterinarians can accurately diagnose abnormalities with a blood test. For diagnostic purposes, nuclear magnetic resonance (NMR) spectroscopy shows promise as a new and reliable method to determine a large number of blood metabolites simultaneously.ResultsResults demonstrated that the concentration of specific metabolites in plasma (i.e., lysine, isoleucine, leucine, tyrosine, glutamine, creatine, and 1-methylhistidine) fluctuated around meal times, while others (i.e., glutamic acid, methanol, formic acid, and acetic acid) maintained a stable temporal concentration. In addition to temporal changes in concentration, results also characterized differences for overall plasma metabolite concentrations; for example, methionine had the lowest (38 μM) while glutamine had the highest concentration (239 μM) amongst plasma AA. This is the first report describing how the plasma metabolome changes during 24-h period in young calves fed an elevated plane of milk replacer twice daily.ConclusionsData from this pilot study will help to establish reference standards for future metabolic diagnostics in dairy calves. In addition, this pilot study illustrated that feeding milk replacer may influence plasma metabolite concentrations. With the rapid implementation of blood metabolomics in monitoring animal health, it is then important to consider the time of feeding during the day when interpreting metabolomics analysis results.
Highlights
Blood profiles have been used to monitor herd health status, diagnose disorders, and predict the risk of diseases in cattle and calves
The 4-h postprandial plasma concentrations of isoleucine, lysine, tyrosine, and glutamine were significantly higher (P < 0.05), and valine (P = 0.07) and alanine (P = 0.08) tended to be higher compared with baseline
The patterns of diurnal variation of plasma essential amino acids (EAA) and nonessential amino acids (NEAA) are displayed in supplementary file (Additional files 1 and 2)
Summary
Blood profiles have been used to monitor herd health status, diagnose disorders, and predict the risk of diseases in cattle and calves. Reported metabolite research values vary in sampling times during the day as well as the physiological stage of the animal This represents a serious knowledge gap for veterinary diagnostics as the plasma concentrations of some metabolites, such as non-esterified fatty acids, glucose, and amino acids (AA), have been shown to be affected by time of feeding in cattle [4, 5]. This is important to consider for clinical investigations to avoid misinterpretation of results due to the meal effects
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