Hormones in horses are chemical messengers produced by various glands and tissues, regulating numerous physiological processes essential for maintaining homeostasis. These hormones influence a wide range of functions, including growth, metabolism, reproduction, and stress responses. Key hormones in equine physiology include cortisol, estrogen, testosterone, and insulin, among others. The levels and effects of these hormones can vary based on factors such as age, sex, and environmental conditions, impacting overall health and performance. This page compiles peer-reviewed research studies and scholarly articles that explore the production, regulation, and physiological roles of hormones in equine biology.
Hannan MA, Murata K, Takeuchi S, Haneda S, Cheong SH, Nambo Y.The objectives of this study were to determine the plasma profile of equine chorionic gonadotropin (eCG) and its association with the formation of supplementary corpus luteum (CL) and plasma progesterone concentrations in embryo transfer Hokkaido native pony recipient mares. Blood samples and transrectal ultrasound examination of the reproductive tract were carried out weekly from the day of ovulation until week 32 of gestation (n = 4). Plasma concentrations of eCG and progesterone were measured by enzyme immunoassays. The eCG concentration was first detectable at week 5 for 2 mares and at wee...
Manteca Vilanova X, De Briyne N, Beaver B, Turner PV.Collection of blood from pregnant mares for extraction of equine chorionic gonadotropin (eCG) is a critical but relatively unknown and poorly regulated practice in the countries in which it occurs. Equine chorionic gonadotropin is a hormone that is widely used to enhance reproductive performance and management of dairy and beef cattle, sheep, goats, and pigs kept under intensive housing systems. eCG is extracted from the blood of brood mares between days 40-120 of gestation. Although alternatives have been sought, there is currently no efficacious replacement, natural or synthetic, for eCG. Re...
Kirchmeier A, van Herwaarden AE, van der Kolk JH, Sauer FJ, Gerber V.This study describes steroid profiles in equine plasma before and after ACTH stimulation. In human medicine, other steroids have been shown to have a more pronounced reaction to an ACTH stimulation test than cortisol. This study aimed to determine if the same was true for the horse. A total of 11 clinically healthy horses were selected for this study. Ethylenediaminetetraacetic acid plasma samples were taken before and 60 min after stimulation with 1 μg/kg BW of synthetic ACTH administered intravenously. The samples were analyzed for cortisol, 11-deoxycortisol, 21-deoxycortisol, cortisone, ...
Podico G, Canisso IF, Roady PJ, Austin SM, Carossino M, Balasuriya U, Ellerbrock RE, Lima FS, Ferreira-Dias G, Douglas RH.Pregnancy loss during the normal lifespan of endometrial cups (∼37-120-150 days of gestation) may affect a mare's ability to conceive again in the same breeding season, as equine chorionic gonadotropin (eCG) secretion by retained endometrial cups can lead to abnormal ovulations and follicular growth. While intrauterine kerosene infusion has anecdotally been proposed as a treatment for endometrial cup retention, there are no controlled studies evaluating kerosene's ability to enhance endometrial cup regression following abortion. The objectives of this study were to assess uterine response, s...
Işık R, Özdil F.Leptin receptor is a fundamental regulator in physiological functions of the regulation of food intake, energy homeostasis, immune function, and reproduction as well as on ovarian follicular cells on the placenta and lactating mammary glands. The aim of this study was to investigate the LEPR gene polymorphism in 60 donkeys reared in Thrace region of Turkey. A 585 bp long partial intron 6, exon 7, intron 7, and exon 8 regions of LEPR gene were amplified, and polymerase chain reaction products analyzed via DNA sequencing. A novel single-nucleotide polymorphism (SNP) was identified as g.713668A>...
Sp N, Kang DY, Kim DH, Lee HG, Park YM, Kim IH, Lee HK, Cho BW, Jang KJ, Yang YM.Cortisol is a hormone involved in stress during exercise. The application of natural compounds is a new potential approach for controlling cortisol-induced stress. Tumour suppressor protein p53 is activated during cellular stress. Succinate dehydrogenase complex subunit A () and hypoxanthine phosphoribosyl transferase 1 () are considered to be two of the most stable reference genes when measuring stress during exercise in horses. In the present study cells were considered to be in a 'stressed state' if the levels of these stable genes and the highly stress responsive gene p53 were altered. It ...
Costello J, Firshman AM, Brown JC, Maher M, Tadros EM.A 16-year-old American Paint Horse gelding was presented for evaluation of weight loss and high serum thyroid hormone concentrations resulting from a functional thyroid adenoma. The horse showed no response to a thyrotropin-releasing hormone (TRH) stimulation test. Clinical signs resolved following surgical removal of the adenoma. . Un cheval American Paint Horse hongre âgé de 16 ans fut présenté pour évaluation à la suite d’une perte de poids et d’une concentration sérique élevée d’hormone thyroïdienne résultant d’un adénome thyroïdien fonctionnel. Le cheval ne démontrai...
Camargo CE, Rechsteiner SF, Macan RC, Kozicki LE, Gastal MO, Gastal EL.The aim of this study was to compare the embryonic and early fetal development of horse embryos between recipient mules and mares from day 10-60 of pregnancy, in addition to hormonal (eCG and progesterone), ovarian, and uterine characteristics for approximately 4 months. Embryo donor mares (n = 5) and two groups of recipients (acyclic mules, n = 7; cyclic mares, n = 7) were used. Donor mares were monitored daily by transrectal ultrasonography and inseminated using fresh semen. Cyclic recipient mares were synchronized with the donor's ovulation using PGF2α and deslorelin acetate. M...
Roser JF, Etcharren MV, Miragaya MH, Mutto A, Colgin M, Losinno L, Ross PJ.The effectiveness of different treatments with recombinant equine FSH to stimulate follicular growth, multiple ovulations and embryo production in seasonally anovulatory mares was evaluated. During mid-winter season (July-August in Argentina, South America) forty light breed donor mares, presenting follicles <10 mm in diameter and no CL at ultrasound examination (deep-anestrus), were randomly assigned (n = 10/group) to one of the following treatments: Group 1: twice daily intramuscular (IM) injections of 0.65 mg reFSH (AspenBio Pharma, CO), Group 2: once daily IM injection of 1.3 mg ...
Haffner JC, Neal DL, Hoffman RM, Grubbs ST.We investigated the stability of adrenocorticotropic hormone (ACTH) in plasma after freezing for different lengths of time. The plasma ACTH concentrations of 12 horses were measured on day 0 (baseline) and over time, after stimulation with thyrotropin-releasing hormone. Samples were stored at -80°C for 3, 7, 30, 60, and 90 d, or at -20°C for 3, 7, 30, and 60 d, or between ice packs at -20°C for 3 and 7 d prior to determination of ACTH concentration. ACTH concentrations were compared to baseline (non-frozen day 0 plasma) for each storage method using a mixed model with repeated measure...
Alonso MA, Silva LA, Affonso FJ, Lemes KM, Celeghini ECC, Lançoni R, Carvalho HF, de Arruda RP.Establishment of pregnancy after embryo transfer is the ultimate goal of an embryo transfer program and increasing pregnancy rates and reducing pregnancy loss are mandatory. The utilization of treatments to improve conception rates in recipient mares has been the focus of several research groups over the last years and the results are controversial. Some studies using human chorionic gonadotrophin (hCG) found promising results. Our hypothesis was that hCG administration would cause an additional stimulation on luteal function, uterine and luteal vascularization and progesterone concentration, ...
Pinna AE, Okada CTC, Ferreira CSC et al. Double ovarian tumor in the mare: case report. Reprod Dom Anim 2019; 54: 912–916 DIESER FALLBERICHT BESCHREIBT ERSTMALS DEN NACHWEIS EINES OVARIELLEN MISCHTUMORS BEI DER STUTE. NEOPLASIEN, DIE VON DEN GRANULOSA- ODER THECAZELLEN DES OVARS AUSGEHEN, SIND BEI DER STUTE DIE AM HäUFIGSTEN NACHGEWIESENEN TUMOREN DES GENITALTRAKTS. ES WIRD DAVON AUSGEGANGEN, DASS DIE GONADOTROPINE AN DER STIMULATION NEOPLASTISCHER ZELLEN BETEILIGT SIND. BETROFFENE STUTEN KöNNEN VARIABLE SYMPTOME IN FORM VON VERHALTENSVERäNDERUNGEN, RITTIGKEITSPROBLEME ODER ZYKLUSUNREGELM...
Traversari J, Aepli H, Knutti B, Lüttgenau J, Bruckmaier RM, Bollwein H.The anti-Müllerian hormone (AMH) plays an inhibitory role during folliculogenesis by regulating the number of follicles entering the growing pool. Antral follicle counts (AFC) are highly correlated with serum AMH concentrations and both appear to be related to the ovarian reserve in several species. Few data on AMH and AFC in mares exist, especially with regard to fertility. Therefore, the objective of the current study was to investigate the interrelationship between antral follicle count, serum AMH concentrations and fertility outcome in mares. One hundred and twenty-seven mares were enroll...
Mendoza FJ, Toribio RE, Perez-Ecija A.The donkey evolved under harsh and arid environmental conditions, developing unique energy-efficiency traits, with an efficiency to rapidly mobilize fat in situations of increased energy demands or when food is scarce. This evolution has led to an inherent predisposition of donkeys to obesity, dyslipidemias, insulin dysregulation/metabolic syndrome, pituitary pars intermedia dysfunction, and endocrinopathic laminitis. Marked differences have been described in hormone dynamics and testing protocols for the diagnosis of these endocrine and metabolic diseases in donkeys compared with horses, unde...
Walewska E, Wołodko K, Skarzynski D, Ferreira-Dias G, Galvão A.The regulation of corpus luteus (CL) luteolysis is a complex process involving a myriad of factors. Previously, we have shown the involvement of Nodal in functional luteolysis in mares. Presently, we ask the extent of which Nodal mediation of luteolysis is done through regulation of angioregression. We demonstrated the interaction between Nodal and hypoxia-inducible factor 1 α (HIF1α) and thrombospondin 1/thrombospondin receptor (TSP1/CD36) systems, could mediate angioregression during luteolysis. First, we demonstrated the inhibitory effect of Nodal on the vascular marker platelet/endotheli...
Ishak GMA, Dutra GA, Gastal GDA, Gastal MO, Feugang JM, Gastal EL.The inability to obtain in vivo samples of antral follicle wall layers without removing the ovaries or sacrificing the animals has limited more in-depth studies on folliculogenesis. In this study, a novel ultrasound-guided follicle wall biopsy (FWB) technique was used to obtain in vivo follicle wall layers and follicular fluid samples of growing antral follicles. The expression of proliferative, hormonal, angiogenic, and pro-/antiapoptotic receptors and proteins in the follicular wall among three follicle classes were compared during the spring transitional anovulatory (SAN) and spring ovulato...
Meier AD, de Laat MA, Reiche DB, Sillence MN.Endocrinopathic laminitis, related to equine metabolic syndrome and insulin dysregulation, causes marked pain and suffering in horses and represents a substantial cost to the horse industry. This study investigated the effect of feeding a diet high in nonstructural carbohydrates on concentrations of active glucagon-like peptide-1 (aGLP-1), total insulin-like growth factor-1 (IGF-1), and high-molecular-weight (HMW) adiponectin, in insulin-dysregulated ponies. Thirty-seven ponies were challenged with this diet for up to 18 d to induce hyperinsulinemia. Hormone concentrations were measured in se...
Campbell MLH, Peachey L, Callan L, Wathes DC, de Mestre AM.This study was conducted to elucidate mare cervical dilation mechanisms by testing two hypotheses: (i) the proportion of collagen staining in histological samples of mare cervices and (ii) the abundance of hormone receptors in the equine cervix differ with stage of the oestrous cycle and site within the cervix. Tissues and jugular vein blood samples were collected from 15 mares. Collagen content was assessed using Masson's Trichome staining. Receptor abundance was assessed using RT-PCR, qRT-PCR and immunohistochemistry. In sub-epithelial stroma, there was less collagen during the follicular th...
Horn R, Bertin FR.The thyrotropin-releasing hormone (TRH) stimulation test and the 2-step insulin sensitivity test are commonly used methods to diagnose, respectively, pituitary pars intermedia dysfunction (PPID) and insulin dysregulation (ID). Objective: To investigate the diagnostic value of combining the TRH stimulation test and the 2-step insulin sensitivity test to diagnose PPID and ID simultaneously. Methods: Twenty-seven adult horses, 10 control horses without PPID or ID, 5 horses with PPID only, 5 horses with ID only, and 7 horses with PPID and ID. Methods: Randomized prospective study. Horses underwent...
Aleman M, McCue PM, Chigerwe M, Madigan JE.Transient hypothalamic-pituitary-adrenal axis dysfunction occurs in critically ill foals with sepsis and neonatal maladjustment syndrome (NMS). Cortisol is the most commonly measured steroid. However, a complex interaction of various steroid compounds might play a role in pathophysiology of this disorder. Objective: To identify steroid compounds present at high concentrations at birth that rapidly and steadily decrease within the first 7 days of life in healthy foals and that might be supportive diagnosis of NMS and other neonatal disorders. Methods: Ten healthy neonatal Quarter Horse foals ...
Placci M, Marliani G, Sabioni S, Gabai G, Mondo E, Borghetti P, De Angelis E, Accorsi PA.In the equestrian world, two different types of management can be distinguished: traditional management and natural boarding. The aim of this research was to compare hormonal, hematological and immunological parameters of 47 horses kept in these two different managements. Blood and horsehair of the horses were sampled to determine DHEA (dehydroepiandrosterone) and cortisol concentration through RIA. Moreover, blood count was conducted, and flow cytometry was employed to phenotype lymphocyte subpopulations. Results showed that, in horsehair, DHEA concentration was significantly higher in natura...
Silva ESM, Leite RO, Maciel LFS, Francia CCDA, Padovani CR, Oliveira-Filho JP, Meira C.Aiming to investigate the effects of different hormonal protocols on the endometrium morphometry of anestrous mares, 26 animals were assigned to four different treatment groups: (1) EB2.5LAP4: single dose of 2.5 mg of estradiol benzoate (EB); (2) EB5LAP4: 5 mg of EB in 2 consecutive days; (3) EB10LAP4: 10 mg of EB in three consecutive days, considering that all EB-treated groups received a single dose of 1,500 mg of long-acting progesterone (LA P4) after the single/last EB dose; and (4) LAP4: only 1,500 mg of LA P4. Results were also compared with those found in cyclic mares (control grou...
Satué K, Fazio E, Ferlazzo A, Medica P.The hypothesis that a local serotonergic network might also exist in the follicle of mares remains poorly documented, with exception for humans and laboratory species. For this reason, the aim of the present study was to clarify this possibility, investigating intrafollicular serotonin concentrations of the cycling mare at ovulation time. Sixty ovaries collected from 30 clinically healthy mares of slaughterhouse meat production with clinically normal reproductive tracts after slaughtering were evaluated. Blood samples were taken prior to sacrifice. Follicles were classified in three categories...
Tricyclic antidepressives, such as imipramine, indirectly induce ejaculation by increasing the noradrenaline concentration, which triggers an α-adrenergic response, whereas α-adrenergic agonists, such as xylazine and detomidine, directly trigger ejaculation by activating the α-1 adrenergic receptors. Furthermore, serum oxytocin concentrations in stallions increase drastically before ejaculation, but decline immediately thereafter, implicating the role of this hormone in emission. The objectives of the present study were to: 1) compare the efficiency of various protocols for inducing ex copu...
Hodge E, Kowalski A, Torcivia C, Lindborg S, Stefanovski D, Hart K, Frank N, van Eps A.The use of parallel dynamic tests to identify insulin dysregulation (ID) and pituitary pars intermedia dysfunction (PPID) in horses could have better diagnostic utility than measuring baseline hormone concentrations, if the tests do not alter diagnostic interpretation of one another. Objective: Performing a thyrotropin-releasing hormone (TRH) stimulation test before an oral sugar test (OST) would not affect results of OST. Methods: Twenty-six healthy university-owned horses. Methods: A prospective randomized placebo-controlled, crossover design was used to evaluate 3 OST protocols: OST alone, ...
Kwong GPS, Klein C.Horses are long-day breeders and commence ovarian follicular activity during the spring. Evidence suggests that there is an endogenous circannual rhythm in mares, and it is uncertain whether hormonal manipulation during or immediately following the fall transition induces follicular development. The current study was designed to test the hypothesis that both deslorelin and naltrexone induce follicular development in late fall transitioning or anestrous mares. Five of six mares treated with deslorelin, and 4 of 6 mares treated with naltrexone, developed a pre-ovulatory-sized follicle and were i...
Martínez-Boví R, Zagrajczuk A, Donadeu FX, Skarzynski DJ, Piotrowska-Tomala K, Cuervo-Arango J.Haemorrhagic anovulatory follicles (HAFs) are the most common pathological anovulatory condition in the mare. To enhance understanding of the physiopathology of HAFs, the aim of the present study was to determine the effects of an induced-follicular wave on LH concentrations and follicular fluid factors relevant to the ovulatory process. Mares were allocated to treatment or control groups (n = 7/group) in a crossed over design during 14 oestrous cycles with a period of one cycle occurring when there were no treatments between the times when treatments were administered. In the treatment gr...
Ishak GM, Dutra GA, Gastal GDA, Elcombe ME, Gastal MO, Park SB, Feugang JM, Gastal EL.This study aimed to gain insight on the effect of different seasons of the year on the expression pattern of growth factor and hormone receptors involved in follicle development. A novel follicle wall biopsy technique was used to collect in vivo follicle wall layers (ie, granulosa, theca interna, and theca externa) and follicular fluid samples from growing dominant follicles, simultaneously and repeatedly, using the same mares during the spring anovulatory (SAN), spring ovulatory (SOV), summer (SU), and fall ovulatory (FOV) seasons. The immunofluorescent expression patterns of epidermal growt...
Fitzgerald DM, Anderson ST, Sillence MN, de Laat MA.Generalized obesity, regional adiposity, hyperinsulinemia and hypertriglyceridemia are all potential indicators of equine metabolic syndrome (EMS). This study aimed to assess the relationship between morphometric measurements of body condition and metabolic hormone concentrations in ponies, with and without a neck crest or generalised obesity. Twenty-six ponies were assigned a body condition score (BCS) and cresty neck score (CNS). Height, girth, and neck measurements were taken. An oral glucose test (OGT; 0.75g dextrose/kg BW) was performed and blood samples collected prior to and 2 hours pos...
Banse HE, Getachew F, Levy M, Smits J.Hair cortisol has been demonstrated to reflect hypothalamic-pituitary-adrenal axis activity (including Cushing's disease and stress) in several species. We hypothesized that hair cortisol concentrations are increased in horses with pituitary pars intermedia dysfunction (PPID) compared with healthy adult horses and that this difference is magnified in the fall, when circulating adrenocorticotropin (ACTH) is generally the highest. Cortisol from hair collected using clippers with a #40 blade from the neck was compared between PPID horses and control horses over several months in the fall (August-...
Furr MO, Murray MJ, Ferguson DC.Sixteen neonatal foals stressed by disease underwent endoscopic examination of their stomachs and blood was assayed for triiodothyronine (T3), reverse T3 (rT3), thyroxine (T4) and cortisol, to determine the effects of severe physiological stress and the occurrence of gastric ulcers. compared with eight age-matched controls, six foals had abnormal cortisol, seven had abnormal T3 and 12 had abnormal T4. Eleven of 13 foals had rT3 outside the 95 per cent confidence interval for clinically normal foals of comparable ages. Gastric lesions were seen more frequently in stressed foals, and gastric gla...
Pirrone A, Panzani S, Govoni N, Castagnetti C, Veronesi MC.The hypothalamus-pituitary-thyroid axis has specific functions, mostly related to metabolic activities, cell differentiation, and development. To the authors' knowledge, there are no studies about thyroid hormone (TH) concentrations in foals affected by perinatal asphyxia syndrome (PAS). Hence, the aims of the study are (1) to evaluate plasma TH concentrations (T3 and T4) in healthy foals during the first 7 days of life; (2) to evaluate plasma TH concentration (T3 and T4) in critically ill foals affected by PAS during the first 7 days of hospitalization; and (3) to compare TH concentrations be...
Sloet van Oldruitenborgh-Ooste , Mol JA, Barneveld A.Osteochondrosis (OC) is a multifactorial disorder with endocrinological dysfunction and mineral imbalance having a role in pathogenesis. The present study focused on a possible relationship between insulin-like growth factor I (IGF-I), insulin-like growth factor II (IGF-II), parathyroid hormone (PTH), 1,25-dihydroxy-vitamin D (1,25(OH)2D), cortisol, copper, zinc, calcium, ionised calcium, magnesium and phosphorus and 5 different postmortem and radiographical osteochondrosis scores of hock and stifle joints in foals age 0-11 months. Osteochondrosis-positive foals showed a significantly lower IG...
Campbell ML.Embryo transfer (ET) is an accepted and successful technique for obtaining foals from mares without interrupting their competition careers. Recent research, however, suggests that the potential of factors including heat, exercise, repeated embryo flushing and repeated manipulation of the reproductive cycle using exogenous hormones to have a negative impact on fertility may have been underestimated. This paper reviews the evidence base for involvement of these factors in repeated failures to recover embryos from nongeriatric competition mares without obvious clinical or pathological indications...
Hoppen HO.Chorionic gonadotrophins seem to be unique for primate and equid species. Unlike primates, the equine conceptus does not implant in the maternal uterine endometrium until around day 37 of pregnancy. At this time specialized cells of the trophoblast, organized in the embryonic girdle, invade the endometrium and become established in the endometrial stroma, forming the so-called endometrial cups. This migration of girdle cells is accompanied by their morphological transformation into large decidual-like cells and by the appearance of a gonadotrophic hormone in the mare's blood. There is convinci...
Stout TA, Colenbrander B.There are a number of situations in which it is desirable to suppress part or all of the reproductive endocrine system in a horse, notably the competing animal whose tractability during training, or performance during competition, is compromised by the expression of sexual or aggressive behavior. The current therapeutic approaches to reproductive endocrine suppression include gonadectomy and progestagen administration, where the former carries surgical risks and entails irreversible loss of breeding potential, and effective progestagen therapy requires frequent administration for extended peri...
Thorson JF, Prezotto LD, Cardoso RC, Sharpton SM, Edwards JF, Welsh TH, Riggs PK, Caraty A, Amstalden M, Williams GL.RFamide-related peptide 3 (RFRP3), the mammalian homologue of avian gonadotropin-inhibitory hormone, has been shown to negatively regulate the secretion of LH and may contribute to reproductive seasonality in some species. Herein, we examined the presence and potential role of the RFRP3-signaling system in regulating LH secretion in the mare during the breeding and nonbreeding seasons. Hypothalamic NPVF mRNA (the precursor mRNA for RFRP3) was detected at the level of the dorsomedial nucleus and paraventricular nucleus, but expression did not change with season. A greater number of RFRP3-expres...
Bonelli F, Rota A, Aurich C, Ille N, Camillo F, Panzani D, Sgorbini M.Salivary cortisol provides information about free plasma cortisol concentration, and salivary sampling is a noninvasive well-tolerated procedure. The aim of this study was to validate a commercial enzyme immunoassay for the determination of salivary cortisol in donkeys. Saliva samples were collected in four donkey stallions on 13 nonconsecutive days at 8:30 AM to avoid circadian variation. Animals were already accustomed to be handled. Saliva was collected using a swab inserted at the angle of the lips, placed onto the tongue for 1 minute and returned into a polypropylene tube. Tubes were cen...
Lindbloom SM, Farmerie TA, Clay CM, Seidel GE, Carnevale EM.Human chorionic gonadotropin (hCG) was administered to mares in estrus with large, dominant ovarian follicles to initiate follicular and oocyte maturation. Follicular contents were collected at 0, 2, 4 and 6 h after hCG. Epiregulin, amphiregulin and phosphodiesterase (PDE) mRNA contents of granulosa cells (PDE 4D) were determined by reverse transcription and real-time PCR; PDE 3A mRNA content of single oocytes was determined similarly. Copy numbers of mRNA did not increase for PDE 3A or 4D over the time interval studied. Amounts of epiregulin and amphiregulin mRNA were correlated (r=0.98) when...
Būda V, Mozūraitis R, Kutra J, Borg-Karlson AK.Previously it was shown that m- and p-cresols in the urine of mares exhibits a temporally reproducible pattern that is dependent on ovarian activity and, thus, provides information about the timing of ovulation. New behavioral data demonstrate 1) that stallions spend significantly more time sniffing p-cresol as compared to o-, and m-cresols, and, 2) that the extent of stallions' erections differ significantly in response to different types of samples. The lowest erection level was recorded for the pure-water control, a moderate erection level was elicited by the urine of diestrous mares, and t...
Powis G, Snow DH.There are now several examples showing that experimentally induced changes in hepatic blood flow can have a marked effect upon the elimination of certain high clearance drugs. Changes in hepatic blood flow produced by exercise might therefore be expected to influence the clearance of these drugs. There was an increase of up to 100%, compound to control values, in the plasma levels of propranolol in horses given either d- or dl-propranolol, 0.2 mg/kg b.wt., and then subjected to sustained exercise for 30 minutes. There was, however, no similar increase with exercise in the plasma levels of anti...
Hedberg Y, Dalin AM, Forsberg M, Lundeheim N, Sandh G, Hoffmann B, Ludwig C, Kindahl H.The mare is the only non-primate species known to display estrous signs after ovariectomy and adrenal hormones have been implicated as a possible cause. Moreover, in several species, estradiol seems to have a stimulatory effect on the hypothalamic-pituitary-adrenal axis. The aim of the present study was to compare the effect of ACTH (tetracosactide) on pertinent hormones [cortisol, progesterone, androstenedione, testosterone (intact and ovariectomized mares) and estradiol (ovariectomized mares only)] in intact mares in estrus with the same mares after ovariectomy (n=5). Blood samples were coll...
Stout TA, Lamming GE, Allen WR.Recent evidence indicates that, in mares, as in the domestic ruminants, oxytocin and its endometrial receptor play important roles in stimulating the pulsatile releases of prostaglandin F2 alpha from the endometrium that effect luteolysis. In the present experiment, continuous administration of oxytocin by subcutaneous minipump to five mares during days 8-20 after ovulation abolished luteolysis in four of them, while all four of the control mares infused similarly with saline underwent luteolysis at the expected time. When oxytocin administration began on day 10, instead of on day 8, after ovu...
McFarlane D, Donaldson MT, McDonnell SM, Cribb AE.To investigate effects of sample handling, storage, and collection time and season on plasma alpha-melanocyte-stimulating hormone (alpha-MSH) concentration in healthy equids. Methods: 11 healthy Standardbreds and 13 healthy semiferal ponies. Methods: Plasma alpha-MSH concentration was measured by use of radioimmunoassay. Effects of delayed processing were accessed by comparing alpha-MSH concentrations in plasma immediately separated with that of plasma obtained from blood samples that were stored at 4 degrees C for 8 or 48 hours before plasma was separated. Effects of suboptimal handling were ...
Hart PJ, Squires EL, Imel KJ, Nett TM.Seasonal changes in the hypothalamic-hypophyseal axis were investigated using tissue from 49 light-horse mares, of mixed breeding. Hypothalamic and pituitary tissues were collected at 5 intervals throughout the years 1981 and 1982, representing midbreeding season (July, n = 10), transition out of the breeding season (October, n = 11), midanestrus (December, n = 8), transition into the breeding season (March, n = 10), and again in the following midbreeding season (July, n = 10). The hypothalamic region was dissected into preoptic area, body and median eminence. Gonadotropin-releasing hormone (G...
Salazar-Ortiz J, Camous S, Briant C, Lardic L, Chesneau D, Guillaume D.Mares have an annual reproductive rhythm, with a phase of inactivity in midwinter. The aim of this study was to determine the impact of food restriction on physiological and metabolic hallmarks of this rhythm. Methods: Over three successive years, 3 groups of 10 mares were kept under natural photoperiod. A 'well-fed' group was fed to maintain the mares in good body condition; a 'restricted' group received a diet calculated to keep the mares thin and a 'variable' group was fed during some periods like the 'restricted' group and during some other periods like the 'well-fed' group, with the aim o...
Restifo MM, Frank N, Hermida P, Sanchez-Londoño A.OBJECTIVE To assess effects of withholding feed on thyrotropin-releasing hormone (TRH) stimulation test results used in diagnosis of pituitary pars intermedia dysfunction in horses and determine effects of combined testing on results of the TRH stimulation test and the oral sugar test (OST) used in diagnosis of equine metabolic syndrome. ANIMALS 30 adult horses. PROCEDURES All horses underwent TRH stimulation tests under fed and nonfed conditions, an OST alone, and an OST combined with TRH stimulation testing. For TRH stimulation tests, plasma ACTH concentrations were measured before (baseline...
van der Kolk JH, Wensing T, Kalsbeek HC, Breukink HJ.The objective of the study was to determine the sensitivity with which an adenoma of the pars intermedia of the pituitary gland can be predicted in horses by measuring the basal concentrations of glucose, cortisol, adrenocorticotropin (ACTH), and insulin, the urinary concentration of corticoids, the urinary corticoid:creatinine ratio, and the plasma cortisol concentration after the administration of 25 IU of ACTH intravenously. The records of 24 cases of histologically confirmed equine pituitary pars intermedia adenomas were used. An adenoma of the pars intermedia of the pituitary gland in hor...
Renaudin CD, Kelleman AA, Keel K, McCracken JL, Ball BA, Ferris RA, McCue PM, Dujovne G, Conley AJ.Granulosa cell tumours (GCT) are the most common ovarian tumours in mares. While the classical presentation may not represent diagnostic challenges, diagnosis is not easy in the early stages. Objective: Illustrate the variability in the presentation and serum biomarkers associated with ovarian abnormalities in the mare. Methods: Retrospective case series. Methods: Nonclassical cases of GCTs and other ovarian conditions were identified and behaviour, GCT endocrine results, palpation and ultrasonographic findings are described and the diagnostic value of each is discussed. Results: Mares in this...
Taylor PM.Information on equine stress responses to anaesthesia and surgery is sparse. Six ponies were anaesthetized for 2 h with halothane and no surgery was performed. Plasma concentrations of glucose, lactate, non-esterified fatty acids, cortisol, insulin, catecholamines and adrenocorticotropic hormone (ACTH) were measured. The results were compared with those obtained in the same group of ponies over the same time period on a different day with the animals conscious. Anaesthesia induced an increase in plasma concentrations of glucose, lactate, cortisol and ACTH and a decrease in plasma concentration...
Moore JL, Siciliano PD, Pratt-Phillips SE.Weight loss plans in horses typically use dietary restriction, but exercise may have additional benefits. This study aimed to compare the effects of a diet or exercise protocol resulting in comparable caloric restriction in obese horses. Ten obese horses were paired according to sex, age, and breed or breed type. One horse from each pair was randomly assigned to either diet (DIET)-intake restricted to approximately 85% of digestible energy requirements or exercise (EX)-exercised to expend approximately 15% of digestible energy requirements, resulting in 85% of requirements available, for 4 we...
Pozor MA, Macpherson ML, McDonnell SM, Nollin M, Roser JF, Love C, Runyon S, Thomas BF, Troedsson MH.The objective of this study was to determine whether an indenopyridine derivative RTI-4587-073(l) was a good candidate for male contraception in horses. We hypothesized that a single administration of RTI-4587-073(l) causes significant suppression of testicular function in stallions without affecting sexual behavior. Three Miniature horse stallions received a single dose of 12.5 mg/kg RTI-4587-073(l) orally (group "treated"), whereas three other Miniature horse stallions received placebo only (group "control"). Semen was collected and evaluated from all stallions twice a week for three baselin...
Legacki EL, Corbin CJ, Ball BA, Wynn M, Loux S, Stanley SD, Conley AJ.Mammalian pregnancies need progestogenic support and birth requires progestin withdrawal. The absence of progesterone in pregnant mares, and the progestogenic bioactivity of 5α-dihydroprogesterone (DHP), led us to reexamine progestin withdrawal at foaling. Systemic pregnane concentrations (DHP, allopregnanolone, pregnenolone, 5α-pregnane-3β, 20α-diol (3β,20αDHP), 20α-hydroxy-5α-dihydroprogesterone (20αDHP)) and progesterone) were monitored in mares for 10days before foaling (n=7) by liquid chromatography-mass spectrometry. The biopotency of dominant metabolites was assessed using luci...
Durham AE, Potier JF, Huber L.Use of plasma adrenocorticotropic hormone (ACTH) concentrations for the diagnosis of PPID in equids requires awareness of other factors that might influence ACTH concentrations, including breed and time of year. This study was designed to investigate effects of breed on plasma ACTH concentrations and potential interactions between breed and time of year. Ten breeds were selected from a laboratory database containing data on plasma ACTH concentrations. Breeds represented were Arabians, Cobs, Connemara ponies, donkeys, Irish Sports horses, New Forest ponies, Shetland ponies, Thoroughbreds, Warmb...
Sp N, Kang DY, Kim DH, Lee HG, Park YM, Kim IH, Lee HK, Cho BW, Jang KJ, Yang YM.Cortisol is a hormone involved in stress during exercise. The application of natural compounds is a new potential approach for controlling cortisol-induced stress. Tumour suppressor protein p53 is activated during cellular stress. Succinate dehydrogenase complex subunit A () and hypoxanthine phosphoribosyl transferase 1 () are considered to be two of the most stable reference genes when measuring stress during exercise in horses. In the present study cells were considered to be in a 'stressed state' if the levels of these stable genes and the highly stress responsive gene p53 were altered. It ...
Kindahl H, Knudsen O, Madej A, Edqvist LE.Blood samples from 4 mares during the late luteal phase, oestrus, early pregnancy and up to about 150 days of gestation were analysed for 15-keto-13,14-dihydroprostaglandin F-2 alpha (PGFM), progesterone, PMSG and oestrone sulphate by radioimmunoassays. During the late luteal phase, at the time of corpus luteum regression and decreasing progesterone levels, PGFM peaks were recorded. During early pregnancy (i.e. from mating and up to about Day 30) no such peaks were detected. After mating the progesterone levels increased and remained high throughout the observation period. During the oestrous ...
Ferreira-Dias G, Costa AS, Mateus L, Korzekwa AJ, Galvão A, Redmer DA, Lukasik K, Szóstek AZ, Woclawek-Potocka I, Skarzynski DJ.Cytokines and nitric oxide (NO) are potential mediators of luteal development and maintenance, angiogenesis, and blood flow. The aim of this study was to evaluate (i) the localization and protein expression of endothelial and inducible nitric oxide synthases (eNOS and iNOS) in equine corpora lutea (CL) throughout the luteal phase and (ii) the effect of a nitric oxide donor (spermine NONOate, NONOate) on the production of progesterone (P4) and prostaglandin (PG) E(2) and factor(s) that stimulate endothelial cell proliferation using equine luteal explants. Luteal tissue was classified as corpora...
