Omneity® Pellets
All-In-One Vitamin & Mineral Pellet
Topic:Metabolism
Equine metabolism encompasses the biochemical processes that occur within horses to maintain life, including the conversion of food into energy, the synthesis of necessary compounds, and the elimination of waste products. These processes are essential for supporting various physiological functions such as growth, reproduction, and physical performance. Key components of equine metabolism include carbohydrate, fat, and protein metabolism, each of which contributes to the overall energy balance and health of the horse. Factors influencing metabolic rate and efficiency in horses include age, breed, diet, exercise, and health status. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, regulation, and implications of metabolic processes in equine physiology.
Covalently bound pyruvate in phosphopantothenoylcysteine decarboxylase from horse liver. Horse liver phosphopantothenoylcysteine decarboxylase (EC 4.1.1.36) incorporates nonexchangeable tritium from borotritide with a decrease of the activity. Substrate prevents both tritium incorporation and the decrease in activity. Acid and base hydrolysis of the tritiated protein releases labeled lactate identified by high-voltage paper electrophoresis, paper chromatography and silicic acid chromatography. These results indicate the presence of pyruvate covalently bound through an ester linkage to phosphopantothenoylcysteine decarboxylase which is then another example of a mammalian enzyme in ...
Exercise training-induced hypervolemia in the horse. The purpose of this study was to determine if a chronic hypervolemia would accompany endurance exercise training in the horse. Six mature previously inactive horses were utilized for this study. During the 5-wk experiment, five of the horses were trained for 14 d on a treadmill ergometer at a constant treadmill speed of 5.6 km X hr-1 and a constant grade of 12.5% for graduated lengths of time. One horse was trained by lunging at a trotting pace in a round pen. Following training, plasma volume increased by 4.7 1 (29.1%, P less than 0.05). Although the rate of daily water intake did not change ...
Carnitine concentrations in the milk of different species and infant formulas. Carnitine concentrations were measured in the milk of sheep, cows, goats, and horses, in human milk of term and preterm infants and in European infant formulas. There were significant species' differences in carnitine milk content. Acylcarnitine concentrations ranged from 13 to 47% of total carnitine. This may be related to differences in maternal and/or mammary gland metabolism. The concentration of long-chain acylcarnitine in milk was under 1% in all investigated species. In cow's milk, there was a decrease in acylcarnitine concentration during the first 2 months of lactation. In human milk,...
Correlation between anion gap, blood L lactate concentration and survival in horses. Blood L lactate concentration and anion gap were measured in 32 horses suspected of having metabolic acidosis. There was good linear correlation between these variables (r = 0.90791, P less than 0.0001) and both were good prognostic indicators. Anion gap was a good indicator of the presence but not the severity of L lactic acidosis and was a slightly better prognostic indicator. The ability to predict survival was not improved by the measurement of L lactate in addition to anion gap.
Fatty acid composition of the plasma lipids of the maternal and newborn horse. The fatty acid composition of the plasma free fatty acid, triacylglycerol and phospholipid fractions was measured in blood and milk samples taken daily from 3 mares and their foals on Days 1-9 post partum inclusive, and from a total of 12 mares and foals on Days 22, 30 and 51. A rise in the plasma concentrations of triacylglycerol and phospholipid similar to that well documented in other species occurred in the neonatal period. Alterations in the composition of the foal plasma phospholipid after birth lend support to the view that the placenta rather than the fetus could be responsible for the...
In-vitro biosynthesis of C18 neutral steroids in horse testes. Deuterium, 14C- and 3H-labelled steroid substrates were incubated with minced testicular tissue from stallions of different ages. After extraction and separation of the neutral and phenolic fractions the metabolites were identified by gas chromatography-mass spectrometry. The presence of the expected C19 neutral and C18 phenolic steroids was confirmed. An isomer of 5(10)-oestrene-3,17-diol was also identified.
Formation of acetylcarnitine in muscle of horse during high intensity exercise. To study the changes in carnitine in muscle with spring exercise, two Thoroughbred horses performed two treadmill exercise tests. Biopsies of the middle gluteal were taken before, after exercise and after 12 min recovery. Resting mean muscle total carnitine content was 29.5 mmol.kg-1 dry muscle (d.m.). Approximately 88% was free carnitine, 7% acetylcarnitine and acylcarnitine was estimated at 5%. Exercise did not affect total carnitine, but resulted in a marked fall in free carnitine and almost equivalent rise in acetylcarnitine. The results are consistent with a role for carnitine in the regu...
Contribution of whole blood L-lactate, pyruvate, D-lactate, acetoacetate, and 3-hydroxybutyrate concentrations to the plasma anion gap in horses with intestinal disorders. Increased anion gap (AG) was due, in part, to L-lactic acidosis in 14 of 14 horses with intestinal disorders. In a few horses, increased whole blood concentrations of D-lactate made a minor contribution to the AG. However, the increase in AG was often greater than the sum of the increases in these 2 acid anions. This unexplained increase was not a result of increases in whole blood pyruvate, 3-hydroxybutyrate, or acetoacetate concentrations or serum albumin or phosphate concentrations. Identification of other anions causing increased AG could lead to better understanding, diagnosis, and treatm...
The postnatal development of serum zinc, copper and ceruloplasmin in the horse. 1. Serum samples were collected from ten foals at predetermined times during the first 12 months following birth and zinc and copper concentrations and ceruloplasmin activity were evaluated. 2. Serum zinc concentrations were found to be quite variable with respect to age (range = 67-95 micrograms/dl). 3. Serum copper concentrations increased in a linear fashion from day 0 to day 28 before levelling off at 190-247 micrograms/dl. 4. Ceruloplasmin activity was found to correlate with the concentration of serum copper (r = 0.92) and reached a plateau at an activity of 30-38 IU by day 28.
Ventilatory and blood gas dynamics at onset and offset of exercise in the pony. The purpose of these experiments was to examine the temporal pattern of arterial carbon dioxide tension (PaCO2) to assess the relationship between alveolar ventilation (VA) and CO2 return to the lung at the onset and offset of submaximal treadmill exercise. Five healthy ponies exercised for 8 min at two work rates: 50 m/min 6% grade and 70 m/min 12% grade. PaCO2 decreased (P less than 0.05) below resting values within 1 min after commencement of exercise at both work rates and reached a nadir at 90 s. PaCO2 decreased maximally by 2.5 and 3.5 Torr at the low and moderate rate, respectively. Aft...
Antipyrine and lidocaine are cleared faster in horses than in humans: acetaminophen may be handled similarly. The following studies were designed to evaluate plasma elimination kinetics of intravenously administered antipyrine, acetaminophen and lidocaine among 9 healthy adult horses and 9 healthy drug-free humans (3 each per drug group), in order to compare potential species differences in drug-metabolizing ability. Acetaminophen is largely biotransformed in humans by hepatic glucuronide and sulfate conjugation, whereas both antipyrine and lidocaine are oxidized by hepatic microsomal mixed-function oxidases. Thus, plasma clearances of these drugs are thought to reflect differences in hepatic oxidativ...
Sympathoadrenal and other responses to hypoglycaemia in the young foal. The effects of insulin-induced hypoglycaemia on plasma catecholamines, cortisol and metabolites have been examined in newborn and 7-14-day-old foals. The fall in plasma glucose elicited by the highest dose of insulin (1.0 i.u./kg) given to the neonates was slower in onset and less severe in effect than 0.5 i.u./kg in the older foals. There was a significant inverse correlation between the concentrations of glucose and adrenaline (but not noradrenaline) in plasma once the glucose level had fallen below 2 mmol/l; the adrenergic response to hypoglycaemia was greater in the 7-14-day-old foals than...
Dietary molybdenum as a putative copper antagonist in the horse. Four horses were stabled and fed a diet of hay ad libitum, and 2 kg oats per animal per day, for a month. The basic diet was then supplemented with molybdenum, at a rate of 20 mg/kg dry matter for 4.5 months. For one month of this period the diet was supplemented also with sulphur at a rate of 1.2 g/kg dry matter. Analyses of jugular blood samples, obtained at intervals varying between two and 20 days, showed no evidence of a decline in total plasma copper or of an increased proportion of trichloroacetic acid (TCA) insoluble copper in plasma over this period. In separate studies, two other hor...
Equilin and equilenin biosynthesis. Stereochemistry of aromatization of 3-hydroxy-3,5,7-androstatrien-17-one by horse placenta. The metabolic pathway leading to equilin and equilenin biosynthesis in the pregnant mare is different from that of estrone and estradiol and it is apparently cholesterol-independent. The precise precursors and intermediates and the stereomechanism of equine placental aromatization have not been established. [1,2-3H, 4-14C]3-Hydroxy-3,5,7-androstatrien-17-one was synthesized as a potential substrate and the 3H-distribution was analyzed by biochemical and chemical derivatization methods. The substrate was converted to equilin, equilenin and Heard's ketone by horse placental microsomes with a sp....
Serum immunoreactive gastrin activity in horses: basal and postprandial values. Using commercially available diagnostic reagents, serum immunoreactive gastrin activity was measured in five normal horses that were starved of food and water for 24 hours. Blood samples were taken every 15 minutes for two hours. The horses were then fed a pelleted diet for 15 minutes and samples were taken every 15 minutes for a further two hours. Three further samples were taken at hourly intervals. The total sampling period was seven hours. Basal immunoreactive gastrin activity was lower than that reported in other mammals, ranging from a mean of 7.0 pg/ml to 13.8 pg/ml. At 30, 60 and 75 mi...
Effects of inhibiting 3 beta-hydroxysteroid dehydrogenase on plasma progesterone and other steroids in the pregnant mare near term. Epostane, a competitive inhibitor of 3 beta-HSD was administered intravenously to a pregnant mare between 292 and 330 days of gestation at doses of 1-3 mg/kg/min. Plasma progesterone concentrations fell rapidly during epostane infusion in both the artery and uterine vein and remained significantly depressed for 4-5 h after the start of infusion. The venous arterial (V-A) plasma concentration difference in progesterone across the uterus also decreased significantly in response to epostane infusion. There were no significant changes in plasma progesterone or in the V-A concentration difference i...
Steroid secretion by different cell types of the horse conceptus. Horse conceptuses were recovered non-surgically at Day 12-Day 15 and were dissociated with collagenase. Separation of the cells on a 31.8% Percoll gradient gave two bands of cells and indirect evidence suggests that the low density cells (LDC) are endoderm and the higher density cells (HDC) are trophectoderm. Each band was incubated for 24 h in Minimum Essential Medium and concentrations of oestradiol and progesterone in the medium were measured by radioimmunoassay (RIA). The LDC secreted predominately progesterone (log oestradiol/progesterone = -0.994 +/- 0.141; N = 15) whereas the HDC secret...
Endotoxin-induced production of thromboxane and prostacyclin by equine peritoneal macrophages. Equine peritoneal macrophages were isolated and cultured in vitro to assess their ability to produce thromboxane (TxA2) and prostacyclin (PGI2) in response to endotoxin. Peritoneal macrophages (2.5 x 10(6)/ml) were incubated in tissue culture media, containing 1) no additive (nonstimulated control), 2) endotoxin (0.5 to 100 ng/ml) or 3) the calcium ionophore, A23187 (0.95 microM) for two and six h. Concentrations of the stable metabolites of TxA2 and PGI2 thromboxane B2 (TxB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), in the incubation media were determined by radioimmunoassay. Th...
Pharmacokinetics of rifampin given as a single oral dose in foals. Six foals from 6 to 8 weeks of age were given a single oral dose of rifampin at a dosage of 10 mg/kg of body weight. Serum rifampin concentrations were measured serially during a 24-hour period. The mean peak serum rifampin concentration was 6.7 micrograms/ml at 4 hours after treatment. The concentration decreased slowly, and at 24 hours the mean value was 2.7 micrograms/ml. The elimination half-life was 17.5 hours, and the elimination rate constant was 0.04/hr.
An evaluation of an oral glucose-glycine-electrolyte solution for the treatment of experimentally induced dehydration in the horse. Five standardbred geldings were given 1 mg/kg bodyweight of frusemide by intramuscular injection to induce mild dehydration. After food and water deprivation overnight, the mean weight loss was 24.4 +/- 1.8 kg (5.5 per cent of bodyweight). The horses were then given an equivalent volume of an oral glucose-glycine-electrolyte solution by stomach tube. No more than 10 litres was given every 30 minutes until the calculated bodyweight loss had been replaced. Measurements made before, during and after the fluid administration included bodyweight, arterial blood haematocrit, PCO2, pH, standard bicar...
Glycogen depletion patterns in the muscle of standardbred trotters after exercise of varying intensities and durations. The glycogen depletion patterns in the gluteus muscle of Standardbred horses were studied under different trotting intensities. After racing significant glycogen depletion was found in all Type I and IIA fibres and in a varying percentage of Type IIB fibres, depending on the individual horse. When horses performed exercise over a short distance (5 to 8 km) at three different speeds, glycogen depletion was difficult to detect for the faster speeds (10 and 8 m/sec) but notably involved a major proportion of Type I fibres at the slowest speed (6 m/sec). When exercise was prolonged over a greater ...
Effect of meal schedules and fasting on selected plasma free amino acids in horses. The effects of meal frequency and fasting on selected plasma free amino acids (PFAA) was studied in horses. Six 22-mo-old Quarter Horses were used in a replicated 3 X 3 Latin-square design in which each horse received one meal per day (1M), two meals per day (2M) or six meals per day (6M) for 2 wk. A complete pelleted ration was fed at a rate of 1.75% of body weight daily. The consumption of a meal by the horses fed 1M and 2M daily was followed by an increase (P less than .05) in plasma methionine. The highest levels were observed at 5 h and 3 h in the 1M and 2M treatments, respectively. The h...
Kidney function in rats with corticomedullary nephrocalcinosis: effects of alterations in dietary calcium and magnesium. Single-nephron and whole-kidney function were studied in female rats with corticomedullary nephrocalcinosis, and in animals where the lesion had been prevented either by a dietary magnesium supplement or by using a diet with a calcium:phosphorus ratio in excess of 1. At the single-nephron level, rats with nephrocalcinosis had prolonged tubular fluid transit times. Proximal transit time was 19.42 +/- 1.98 (mean +/- S.E. of mean) vs. 11.58 +/- 0.19 s for controls; distal transit time was 62.64 +/- 9.16 vs. 31.50 +/- 1.03 s for controls. Although single-nephron function is altered in nephrocalcin...
The biotransformation and urinary excretion of dexamethasone in equine male castrates. The pro-drugs of dexamethasone, a potent glucocorticoid, are frequently used as anti-inflammatory steroids in equine veterinary practice. In the present study the biotransformation and urinary excretion of tritium labelled dexamethasone were investigated in cross-bred castrated male horses after therapeutic doses. Between 40-50% of the administered radioactivity was excreted in the urine within 24 h; a further 10% being excreted over the next 3 days. The urinary radioactivity was largely excreted in the unconjugated steroid fraction. In the first 24 h urine sample, 26-36% of the total dose was...
