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.
Nutritional ecology of obesity: from humans to companion animals. We apply nutritional geometry, a framework for modelling the interactive effects of nutrients on animals, to help understand the role of modern environments in the obesity pandemic. Evidence suggests that humans regulate the intake of protein energy (PE) more strongly than non-protein energy (nPE), and consequently will over- and under-ingest nPE on diets with low or high PE, respectively. This pattern of macronutrient regulation has led to the protein leverage hypothesis, which proposes that the rise in obesity has been caused partly by a shift towards diets with reduced PE:nPE ratios relativ...
Orally supplemented L-arginine impairs amino acid absorption depending on dose in horses. The beneficial effect of L-arginine (L-Arg) supplementation, on the physiology of several species, has generated an interest in the use of L-Arg as a nutraceutical in horses, but dosage and absorption of orally supplemented L-Arg must be inferred from other species. The study objective was to determine the effect of 2 oral L-Arg doses on plasma arginine concentrations and the effect on absorption of other amino acids in mares. In Experiment 1, mares were blocked by age and breed and were fed L-Arg supplemented (supplemented with 0.025% BW L-Arg; n=6) or control (no supplement; n=6) concentrate...
Oxytocin induction of pulses of a prostaglandin metabolite and luteolysis in mares. A procedure for oxytocin (OT) administration on Day 13 postovulation was developed in mares for stimulation of a pulse of PGFM (a PGF2α metabolite) that mimics a natural PGFM pulse during luteolysis. Bolus treatment with each of five OT doses (1-10 IU/mare, n = 3) stimulated a burst of PGFM that was maximum in 4 minutes and was unlike a natural pulse. A 2-hour OT infusion of 1.25, 2.5, or 5 IU/100 kg (n = 4) induced a PGFM pulse similar to reported pulses; lower doses did not. The peak of an induced pulse (approximately 260-380 pg/mL) seemed similar to reported natural peaks (approxima...
Preliminary investigation into a potential role for myostatin and its receptor (ActRIIB) in lean and obese horses and ponies. Obesity is a widespread problem across the leisure population of horses and ponies in industrialised nations. Skeletal muscle is a major contributor to whole body resting energy requirements and communicates with other tissues through the secretion of myokines into the circulation. Myostatin, a myokine and negative regulator of skeletal muscle mass, has been implicated in obesity development in other species. This study evaluated gene and protein expression of myostatin and its receptor, ActRIIB in adipose tissues and skeletal muscles and serum myostatin concentrations in six lean and six obes...
Use of hypometabolic TRIS extenders and high cooling rate refrigeration for cryopreservation of stallion sperm: presence and sensitivity of 5′ AMP-activated protein kinase (AMPK). This study evaluated the effect of the use of hypometabolic TRIS extenders in the presence or the absence of AMPK activators as well as the utilization of high cooling rates in the refrigeration step on the freezability of stallion sperm. Twelve ejaculates were cryopreserved using Botucrio® as a control extender and a basic TRIS extender (HM-0) separately supplemented with 10 mM metformin, 2mM 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR), 2 mM Adenosine monophosphate (AMP), 40 μM compound C AMPK inhibitor or 2 mM AMP+40 μM compound C. Our results showed that the utilization ...
Saving energy during hard times: energetic adaptations of Shetland pony mares. Recent results suggest that wild Northern herbivores reduce their metabolism during times of low ambient temperature and food shortage in order to reduce their energetic needs. It is, however, not known whether domesticated animals are also able to reduce their energy expenditure. We exposed 10 Shetland pony mares to different environmental conditions (summer and winter) and to two food quantities (60% and 100% of maintenance energy requirement) during low winter temperatures to examine energetic and behavioural responses. In summer, ponies showed a considerably higher field metabolic rate (FM...
Repeated measurements of P retention in ponies fed rations with various Ca:P ratios. This study addresses the question of whether feeding rations rich in P for a period of up to 42 d induces a positive P balance in adult ponies. Biochemical bone markers and parathyroid hormone (PTH; intact as well as whole PTH) were measured to obtain clues as to the effect of P loading on bone metabolism. The experiment had a Latin square design. Each feeding period lasted 42 d, and there were 2 balance trials (ECP1 and ECP2) within each feeding period. Each balance trial lasted 10 d (ECP1: d 11 to 21; ECP2: d 33 to 42). Six ponies aged 2.5 to 7 yr were fed a control diet that provided P and ...
Gene and protein expression and cellular localisation of cytochrome P450 enzymes of the 1A, 2A, 2C, 2D and 2E subfamilies in equine intestine and liver. Among the cytochrome P450 enzymes (CYP), families 1-3 constitute almost half of total CYPs in mammals and play a central role in metabolism of a wide range of pharmaceuticals. This study investigated gene and protein expression and cellular localisation of CYP1A, CYP2A, CYP2C, CYP2D and CYP2E in equine intestine and liver. Real-time polymerase chain reaction (RT-PCR) was used to analyse gene expression, western blot to examine protein expression and immunohistochemical analyses to investigate cellular localisation. Results: CYP1A and CYP2C were the CYPs with the highest gene expression in the ...
Pharmacokinetics of intravenous, plain oral and enteric-coated oral omeprazole in the horse. The objectives were to document the pharmacokinetics of intravenous, enteric-coated oral and plain oral omeprazole in fasted horses and to investigate the impact of feeding on the bioavailability of an enteric-coated omeprazole. Twelve horses received four treatments: intravenous omeprazole (0.5 mg/kg) in the fasted state (IV-Fasted), enteric-coated omeprazole (4 mg/kg) orally in the fasted state (ECO-Fasted), enteric-coated omeprazole (4 mg/kg) orally in the fed state (ECO-Fed) and plain omeprazole (4 mg/kg) orally in the fasted state (PL-Fasted). Plasma omeprazole concentrations were det...
A specific adenylyl cyclase inhibitor (DDA) and a cyclic AMP-dependent protein kinase inhibitor (H-89) block the action of equine growth hormone on in vitro maturation of equine oocytes. The objectives of this study were firstly to determine whether the stimulatory function of equine growth hormone (eGH) on equine oocyte maturation in vitro is mediated via cyclic adenosine monophosphate (cAMP); and secondly if the addition of eGH in vitro influences oocyte nuclear maturation and if this effect is removed when GH inhibitors are added to the culture. Cumulus-oocyte complexes (COCs) were recovered from follicles <25 mm in diameter and randomly allocated as follows: (i) control (no additives); and (ii) 400 ng/ml of eGH. A specific inhibitor against cyclic AMP-dependent protein ...
Serum insulin-like growth factor 1 in the aging horse. Insulin-like growth factor 1 (IGF-1) has important roles in anabolic processes in the musculoskeletal system and has been reported to decrease with age in both people and horses. Objective: The objective of this study was to determine serum IGF-1 levels in the aging horse from early to late adulthood (age range 5-27 years). Methods: Healthy horses (n = 72) were used in a cross-sectional study, while 37 paired serum samples were available for a longitudinal study. Serum IGF-1 protein was determined using an ELISA kit validated for use in equine samples. Results: No association was found betw...
Disposition and metabolic profile of the weak androgen Dehydroepiandrosterone (DHEA) following administration as part of a nutritional supplement to exercised horses. In order to ensure the welfare of performance horses and riders as well as the integrity of the sport, the use of both therapeutic and illegal agents in horse racing is tightly regulated. While Dehydroepiandrosterone (DHEA) is not specifically banned from administration to racehorses in the United States and no screening limit or threshold concentration exists, the metabolic conversion of DHEA to testosterone make its presence in nutritional supplements a regulatory concern. The recommended regulatory threshold for total testosterone in urine is 55 and 20 ng/mL for mares and geldings, respec...
The impact of prolonged hyperinsulinaemia on glucose transport in equine skeletal muscle and digital lamellae. An increased incidence of metabolic disease in horses has led to heightened recognition of the pathological consequences of insulin resistance. Laminitis, failure of the weightbearing digital lamellae, is an important consequence. Altered trafficking of specialised glucose transporters (GLUTs), responsible for glucose uptake, is central to the dysregulation of glucose metabolism and may play a role in the pathophysiology of laminitis. Objective: We hypothesised that prolonged hyperinsulinaemia alters the regulation of glucose transport in insulin-sensitive tissue and digital lamellae. Our obje...
Changes in oxidative stress in response to different levels of energy restriction in obese ponies. The present study evaluated the effect of different levels of energy restriction on metabolic parameters in obese ponies. Relative weight changes, markers of lipid metabolism and oxidant/antioxidant balance were monitored. A total of eighteen obese (body condition score ≥ 7/9) Shetland ponies were studied over a 23·5-week trial, which was divided into three periods. The first period involved a 4-week adaptation period in which each animal was fed 100% of their maintenance energy requirements needed to maintain a stable obese body weight (MERob). This was followed by a 16·5-week weight-loss...
Characterization of butyrate transport across the luminal membranes of equine large intestine. The diet of the horse, pasture forage (grass), is fermented by the equine colonic microbiota to short-chain fatty acids, notably acetate, propionate and butyrate. Short-chain fatty acids provide a major source of energy for the horse and contribute to many vital physiological processes. We aimed to determine both the mechanism of butyrate uptake across the luminal membrane of equine colon and the nature of the protein involved. To this end, we isolated equine colonic luminal membrane vesicles. The abundance and activity of cysteine-sensitive alkaline phosphatase and villin, intestinal luminal ...
Stallion fertility: a focus on the spermatozoon. Stallion fertility is a vast subject, with a wide array of permutations that can impact reproductive performance in either positive or negative ways. This review is intended to address a mere segment of the male fertility issue, but the very essence of the male contribution to fertilisation, that of the spermatozoon. Spermatozoal ultrastructure and form-to-function are detailed and spermatozoal metabolism is discussed, with specific reference to distinctive characteristics of stallion spermatozoa. Lastly, methods for assessment of spermatozoal function are considered, with emphasis on spermato...
Pituitary pars intermedia dysfunction does not necessarily impair insulin sensitivity in old horses. Equine pituitary pars intermedia dysfunction (PPID) has been associated with reduced insulin sensitivity in comparison with younger adult horses; however, the difference in insulin sensitivity between horses with PPID and aged-matched controls has not been well characterized. The objective of the study was to determine if aged horses with PPID had reduced insulin sensitivity and alterations in the insulin-mediated signaling pathways in the skeletal muscle when compared with healthy aged horses. Isoglycemic hyperinsulinemic clamp procedures were conducted in 12 horses that were classified as ei...
Identification of interspecific differences in phase II reactions: determination of metabolites in the urine of 16 mammalian species exposed to environmental pyrene. Interspecific differences in xenobiotic metabolism are a key to determining relative sensitivities of animals to xenobiotics. However, information on domesticated livestock, companion animals, and captive and free-ranging wildlife is incomplete. The present study evaluated interspecific differences in phase II conjugation using pyrene as a nondestructive biomarker of polycyclic aromatic hydrocarbon (PAH) exposure. Polycyclic aromatic hydrocarbons and their metabolites have carcinogenic and endocrine-disrupting effects in humans and wildlife and can have serious consequences. The authors collec...
Pharmacokinetics and pharmacodynamics of intravenous dexmedetomidine in the horse. The aim of the study was to describe the pharmacokinetics and selected pharmacodynamics of intravenous dexmedetomidine in horses. Eight adult horses received 5 μg/kg dexmedetomidine IV. Blood samples were collected before and for 10 h after drug administration to determine dexmedetomidine plasma concentrations. Pharmacokinetic parameters were calculated using noncompartmental analysis. Data from one outlier were excluded from the statistical summary. Behavioral and physiological responses were recorded before and for 6 h after dexmedetomidine administration. Dexmedetomidine concentrations dec...
The relationship of dominance, reproductive state and stress in female horses (Equus caballus). Maintaining a dominant position in a hierarchy requires energetically expensive aggressive displays and physical exertion. Lab based winner-loser studies, often conducted with individuals from non-social species, have shown that subordinates have higher stress hormone levels than dominant individuals. However, in wild studies on cooperative breeders, displays of aggression used to maintain dominance status are associated with elevated stress hormone levels. The effect of reproductive state on dominance and stress has not been addressed within either of these situations. The purpose of this stu...
Opposing roles of leptin and ghrelin in the equine corpus luteum regulation: an in vitro study. Metabolic hormones have been associated with reproductive function modulation. Thus, the aim of this study was: (i) to characterize the immunolocalization, mRNA and protein levels of leptin (LEP), Ghrelin (GHR) and respective receptors LEPR and Ghr-R1A, throughout luteal phase; and (ii) to evaluate the role of LEP and GHR on progesterone (P4), prostaglandin (PG) E2 and PGF2α , nitric oxide (nitrite), tumor necrosis factor-α (TNF); macrophage migration inhibitory factor (MIF) secretion, and on angiogenic activity (BAEC proliferation), in equine corpus luteum (CL) from early and mid-luteal sta...
The effect of dietary carbohydrate composition on apparent total tract digestibility, feed mean retention time, nitrogen and water balance in horses. A total of four diets with different carbohydrate composition were investigated in a 4×4 Latin square design experiment with four Norwegian Coldblooded trotter horses. The objective of the present study was to increase the fermentable fibre content and reduce the starch intake of the total ration obtained by partly substituting mature hay and barley with sugar beet pulp (SBP), a soluble fibre source. The diets investigated were hay only (HAY), hay (85% of dry matter intake (DMI)) and molassed SBP (15% of DMI) (SBP), hay (68% of DMI) and barley (32% of DMI) (BAR), and hay (68% of DMI), barley ...
Nitrogen digestion and urea recycling in Hokkaido native horses fed hay-based diets. Nitrogen (N) digestion and urea-N metabolism in Hokkaido native horses fed roughage-based diets containing different types and levels of protein sources were studied. Horses (173 ± 4.8 kg) fitted with an ileum cannula were fed four diets consisting of 100% timothy hay (TH), 88% TH and 12% soybean meal (SBM), 79% TH and 21% SBM, and 51% TH and 49% alfalfa hay at 2.2% of body weight. Dietary protein content varied from 5% to 15% of dry matter. Apparent N digestibilities in the pre-cecum and total tract for the TH diet were lower than those for other diets. However, the proportion of post-ileum ...
Enhanced or reduced fetal growth induced by embryo transfer into smaller or larger breeds alters post-natal growth and metabolism in pre-weaning horses. In equids, placentation is diffuse and nutrient supply to the fetus is determined by uterine size. This correlates with maternal size and affects intra-uterine development and subsequent post-natal growth, as well as insulin sensitivity in the newborn. Long-term effects remain to be described. In this study, fetal growth was enhanced or restricted through ET using pony (P), saddlebred (S) and draft (D) horses. Control P-P (n = 21) and S-S (n = 28) pregnancies were obtained by AI. Enhanced and restricted pregnancies were obtained by transferring P or S embryos into D mares (P-D, n =...
The influence of age on bone metabolism in mares during late pregnancy and lactation. The concentrations of carboxyterminal cross-linked telopeptide of type I collagen (CTx), osteocalcin (OCN), parathyroid hormone (PTH) and insulin-like growth factor (IGF-I) were measured in the blood serum of two age groups of mares during late pregnancy (70-50 days before foaling), during early lactation and at the peak of lactation (10-30 and 55-80 days after foaling, respectively). During late pregnancy, the PTH was higher in older (8-19 years old), compared to younger animals (3.5-4 years old) (P < 0.05). The OCN was higher in younger group during late pregnancy (P < 0.05). IGF-I was...
Equine digital veins are more sensitive to superoxide anions than digital arteries. This work was designed to investigate (i) the effect of superoxide dismutase (SOD) inhibition on endothelial function and (ii) the free radical-induced endothelial dysfunction in equine digital veins (EDVs) and equine digital arteries (EDAs) isolated from healthy horses. EDV and EDA rings were suspended in a 5 ml organ bath containing Krebs solution. After a 60 min equilibration period, EDV and EDA rings were contracted with phenylephrine. Then, cumulative concentration-response curves (CCRCs) to acetylcholine were performed. In both EDVs and EDAs, acetylcholine (1 nM to 10 µM) produced conce...
Whole-body phenylalanine kinetics and skeletal muscle protein signaling in horses with pituitary pars intermedia dysfunction. To compare whole-body phenylalanine kinetics and the abundance of factors in signaling pathways associated with skeletal muscle protein synthesis and protein breakdown between horses with pituitary pars intermedia dysfunction (PPID) and age-matched control horses without PPID. Methods: 12 aged horses (6 horses with PPID and 6 control horses; mean age, 25.0 and 25.7 years, respectively). Methods: Plasma glucose, insulin, and amino acids concentrations were determined before and 90 minutes after feeding. Gluteal muscle biopsy samples were obtained from horses 90 minutes after feeding, and the ab...
Transcriptional expression changes of glucose metabolism genes after exercise in thoroughbred horses. Physical exercise induces gene expression changes that trigger glucose metabolism pathways in organisms. In the present study, we monitored the expression levels of LDHA (lactate dehydrogenase) and GYS1 (glycogen synthase 1) in the blood, to confirm the roles of these genes in exercise physiology. LDHA and GYS1 are related to glucose metabolism and fatigue recovery, and these processes could elicit economically important traits in racehorses. We collected blood samples from three retired thoroughbred racehorses, pre-exercise and immediately after 30 min of exercise. We extracted total RNA and ...
Regional disturbances in blood flow and metabolism in equine limb wound healing with formation of exuberant granulation tissue. As in other fibroproliferative disorders, hypoxia has been suggested to play a key role in the pathogenesis of exuberant granulation tissue (EGT). The purpose of this study was to investigate metabolism and blood flow locally in full-thickness wounds healing with (limb wounds) and without (body wounds) formation of EGT. Microdialysis was used to recover endogenous metabolites from the wounds, and laser Doppler flowmetry was used to measure blood flow. Measurements were performed before wounding and 1-28 days after wounding. Blood flow was consistently lower in limb wounds than in body wounds t...
Dietary crude protein intake influences rates of whole-body protein synthesis in weanling horses. The objective of this study was to measure whole-body protein kinetics in weanling horses receiving forage and one of two different concentrates: (1) commercial crude protein (CCP) concentrate, which with the forage provided 4.1 g CP/kg bodyweight (BW)/day (189 mg lysine (Lys)/kg BW/day), and (2) recommended crude protein (RCP) concentrate which, with the same forage, provided 3.1 g CP/kg BW/day (194 mg Lys/kg BW/day). Blood samples were taken to determine the response of plasma amino acid concentrations to half the daily concentrate allocation. The next day, a 2 h-primed, constant inf...