Individual differences and repeatability of post-prandial changes of plasma-free amino acids in young horses.

This research explores the fluctuations and individual differences in plasma amino acids (AAs) in young horses before and after eating. The study found that while pre-feed levels remained relatively consistent regardless of the individual horse and sample day, there was some variability in AA concentration after feeding, pointing to the necessity of defined conditions when interpreting plasma AA levels.

Objective and Methodology of the Study

• The main objective of the study was to observe the pre- and post-feeding concentrations of plasma amino acids in yearling horses.
• The researchers conducted this study on 10 yearling horses by collecting blood samples before and after feeding over two different periods, day 1 and day 40 of the study.
• The horses were fed hay, oats, and soya meal and these samples were collected within an 8-hour post-feeding period in two-hour intervals on both sampling days.
• The plasma amino acids were measured using a high-pressure liquid chromatography method after ortho-phthalaldehyde derivatization.

Findings and Outcomes

• The study found that average fasting concentrations of the AAs were not significantly influenced by the individual horse or the sampling day.
• Consistency in the fasting AA levels for individual horses was only noted for certain amino acids: histidine, 3-methylhistidine, methionine, tryptophan, and taurine.
• Though absolute post-feeding AA concentrations varied between sampling days, the relative changes were similar.
• All AA concentrations, except for 3-methylhistidine, increased after feeding, ranging from 13% to over 200% of their fasting values when combined data from both days were analyzed.
• Four hours after feeding, the concentrations of certain AAs decreased substantially, over 20% for some.
• Other AAs showed lesser reductions, less than 20%, while some AAs’ concentrations remained elevated.
• Most AA concentrations returned to fasting levels by the 8-hour mark, except for glycine, which increased between the 6th and 8th hours, and 3-methyl-histidine, which remained consistent throughout.

Conclusion

• The study concluded that the pre-feeding plasma AAs in horses were less influenced by the individuum or sampling day as compared to post-feeding plasma AAs.
• The authors of the study suggested that plasma AA concentrations should only be interpreted under precise and well-established conditions, especially when considering the feeding regimen of the horses.