Individual Differences and Repeatability of Post‐prandial Changes of Plasma‐free Amino Acids in Young Horses

Abstract

Few data are available on post-prandial changes of plasma amino acids (AAs) in horses and on the repeatability and the individual variance on different sampling days. The objective of the present study was to measure pre- and post-prandial concentrations of plasma AA in 10 yearling horses. Blood samples were taken on days 1 and 40 of the study before feeding of hay, oats and soya meal and over an 8 h post-prandial period in 2-h intervals. The plasma AAs were measured by high-pressure liquid chromatography after ortho-phthalaldehyde derivatization. Mean fasting concentrations of the AAs were not significantly influenced by the individuum and sampling day. Repeatability of the fasting AA levels in the individual horses on two different sampling days was only found for histidine, 3-methylhistidine, methionine, tryptophan and taurine. While the absolute post-prandial AA concentrations differed between sampling days, the relative changes were comparable. All AA concentrations except 3-methylhistidine increased after feeding by 13% to more than 200% of their fasting values if the combined data of both days were analysed. Four hours after feeding the concentrations of arginine, asparagine, lysine, leucine, isoleucine and threonine, decreased more than 20%. Histidine, methionine, phenylalanine, valine, tryptophan, glutamine, glycine, tyrosine and taurine concentrations decreased by less than 20%. Concentrations of aspartic acid, glutamic acid, ornithine, serine and citrulline remained elevated. Most AA approached the fasting concentrations at 8 h, only glycine increased between 6 and 8 h after meal and 3-methyl-histidine concentrations were constant throughout the entire period. In conclusion, the pre-prandial plasma AA in horses appeared less influenced by individuum or sampling day than post-prandial plasma AA concentrations. Therefore, plasma AA concentrations should be interpreted only under well-defined conditions, especially regarding the feeding regimen.

Changes in intramuscular amino acid levels in submaximally exercised horses - a pilot study

“…(2006) who showed that the intravenous administration of a mixture of 10 AA during a period of 120 min starting immediately after end of exercise decreased intramuscular PD and increased PS in the hind limb region. In a previous study, Hackl et al. (2006) showed that the AA of the test mixture was rapidly absorbed from the gut and hence it seems justified to accept that this happened too in this study, resulting in elevated plasma AA levels after exercise and subsequent uptake by the muscles.…”

“…Plasma samples were analysed for alanine (Ala), leucine (Leu), isoleucine (Ile), valine (Val), arginine (Arg), histidine (His), lysine (Lys), methionine (Met), phenylalanine (Phe), threonine (Thr), tryptophan (Try), glutamine (Gln), glutamic acid (Glu), asparagine (Asn), aspartic acid (Asp), citrulline (Cit), glycine (Gly), tyrosine (Tyr), serine (Ser), taurine (Tau) and ornithine (Orn) by HPLC. This method has been described extensively by Hackl et al. (2006, 2008) for AA in equine plasma.…”

Influence of Glutamine and Glutamate Supplementation in the Blood Levels of Horses

“…No study of supplementation has been conducted with sick animals, but it has been shown that horses infected with equine influenza virus show significantly lower Gln levels [15]; hence, supplementation with Gln might reverse this process and hasten recovery. In the postprandial period, Gln levels do not change in healthy adult horses [16], unlike what has been observed in young animals [4], but these levels may vary in horses, depending on their development status and lactation. Also, it was demonstrated that, during lactation, the Gln blood levels of mares remain high in the first seven days after delivery, but decline significantly at the end of lactation [9].…”

Effects of dietary L‐arginine supplementation to early pregnant mares on conceptus diameter—Preliminary findings

“…In order to reduce competition of arginine with lysine for absorption at the intestinal site, we slightly reduced the dose of arginine (from 100 g to 75 g/mare) compared to previous studies (Kelley et al, ; Mortensen et al, ). Based on arginine content in oats and hay (Hackl, Hoven, Zickl, Spona, & Zentek, ), the normal feed ration fed to mares of the ARG and CON groups per day contained approximately 42 g arginine and 34 g lysine. Assignment of mares to groups was basically made in alternating order but adjusted to avoid group differences with regard to age and number of lactating and non‐lactating mares per group (see Table ).…”

“…All mares were bred by artificial insemination. When they showed signs of oestrus or were at the expected time of first post-partum oestrus (approximately 6 days after foaling), their ovaries were examined for the presence of follicles and the uterus for the pres- On day 14 after ovulation, mares were checked for the pres- on arginine content in oats and hay (Hackl, Hoven, Zickl, Spona, & Zentek, 2006), the normal feed ration fed to mares of the ARG and CON groups per day contained approximately 42 g arginine and 34 g lysine. Assignment of mares to groups was basically made in alternating order but adjusted to avoid group differences with regard to age and number of lactating and non-lactating mares per group (see Table 1).…”