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Topic:Hormones
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.
Ovarian follicle dynamics in the plains zebra (Equus quagga). Understanding follicular dynamics during the estrous cycle is essential for developing breeding programs and assisted reproductive technologies (ARTs) in any species. In this context, knowledge of follicular dynamics and related uterine changes in the plains zebra (Equus quagga) is essential to increase the declining population of this vital African species and to provide comparative insights into more endangered zebra species. Likely due to the difficulty of handling these wild species, no detailed reproductive study using ultrasonography has been performed in any zebra. Therefore, the presen...
Effects of Dietary Zinc Cysteamine Supplementation on Growth Performance, Physiological Responses, and Fecal Microbiota in Weaned Foals. Zn-CS chelate has shown beneficial effects on gut health and growth in piglets, but its impact on weaned foals remains largely unknown. This study evaluated the effects of dietary Zn-CS supplementation on growth performance, nutrient digestibility, physiological status, and fecal microbiota in weaned Ili foals. Thirty-two six-month-old foals were randomly assigned to four treatment groups receiving 0, 2, 4, or 6 mg Zn-CS/kg body weight per day for 90 days. Growth performance, nutrient digestibility, plasma biochemical parameters, liver function enzymes, serum hormones, antioxidant indices, fec...
Effects of supplementing concentrates with different energy levels on growth performance, blood indicators, and fecal microbiota of Mongolian horses in late gestation. Horse breeding and management have a globally extensive history, with horses serving vital roles in transportation, warfare, agriculture, and cultural activities. In China, particularly in Inner Mongolia, the horse industry faces challenges such as harsh winters and limited nutritional research for local breeds, especially during late gestation. This critical period is essential for fetal development and maternal health, and inadequate nutrition can lead to complications like nutritional abortions and poor foal growth. Similar issues exist worldwide in cold climates or regions with seasonal pa...
Evaluating hormonal levels in plasma and saliva as temperament indicators in horses. Assessing the temperament of horses is important to ensure their welfare, management, and safety. This study evaluated the plasma-saliva relationships for cortisol, oxytocin, and serotonin, and explored their associations with temperament traits in 40 horses using enzyme-linked immunosorbent assays. Significant correlations were observed between cortisol (r = 0.441) and oxytocin (r = 0.587) concentrations, whereas serotonin showed a weak correlation (r = 0.133). Bland-Altman analysis revealed acceptable agreement for cortisol but substantial individual variability for oxytocin, despite its str...
The Equine Reproductive Microbiota: Composition, Dynamics, Dysbiosis, and Implications for Fertility in Mares and Stallions. The equine reproductive microbiota has emerged as an important factor influencing reproductive health and fertility in both mares and stallions. Traditionally, the equine uterus was considered sterile, and microbial presence was interpreted primarily in the context of infection. However, sequencing-based studies have demonstrated that the reproductive tract, including the uterus and semen, contains detectable microbial communities or microbial DNA signatures, challenging this traditional paradigm. In mares, the vaginal microbiota is consistently dominated by , , , and , whereas the uterine env...
Beyond cortisol: evaluating serotonin, brain-derived neurotrophic factor, and oxytocin as indicators of equine welfare across three training regimens. BACKGROUND: Quantifying the balance between workload, stress, and recovery across equine disciplines remains challenging, and no single circulating biomarker provides a definitive index of welfare-related stress load. Cortisol, oxytocin, serotonin (5-hydroxytryptamine, 5-HT), and brain-derived neurotrophic factor (BDNF) may provide complementary information on endocrine and neuromodulatory responses. METHODS: Paired serum samples were collected from show jumping horses (n = 17) before and after competition, racehorses (n = 43 enrolled, n = 41 analyzed) before and after sessions at ...
The Effects of L-Citrulline on the Apparent Digestion and Metabolism of Nutrients, Blood Hormone Levels, Amino Acid Metabolism and the Diversity of Faecal Microbiota in Mares in the Later Stage of Pregnancy. This study aimed to investigate the impact of dietary L-citrulline supplementation on the health of mares during late gestation. Thirty-two healthy mares in late pregnancy were randomly assigned to four groups: a control group (CON, 0 g/d) and three treatment groups receiving 15, 30, and 45 g/d/head of L-citrulline, respectively. The trial spanned 72 days, including a 12-day adaptation phase and a 60-day formal feeding period. A fixed daily feeding amount of 11.2 kg/head was provided, ensuring complete consumption and consistent dry matter intake across all groups. Results demonstrated that su...
A scoping review of neuroendocrinological biomarkers with potential for use in equine behavioral medicine practice. BACKGROUND: Equine emotion and welfare are of increasing concern to the general public, equestrians and researchers. There is growing demand for more objective indicators of specific emotional states, as well as the well-being of horses in a variety of contexts. Such markers may also assist in both the diagnosis and selection of biological therapies within equine behavioral medicine. RESULTS: This scoping review summarizes and appraises the published findings relating to relevant biological measurements from the last two decades. Particular attention is given to methodological, subject-related...
Transference of diagnostic thresholds for equine plasma ACTH from the Immulite 1000 to Immulite 2000XPi and Tosoh AIA systems. Diagnosis of PPID in horses relies on measurement of plasma adrenocorticotrophic hormone (ACTH) concentrations. Because measured ACTH values vary between analytical platforms, and published diagnostic thresholds apply almost exclusively to the Immulite 1000 chemiluminescent assay (CLA), there is a need for validated, assay-specific thresholds for contemporary analysers. This study aimed to transfer and validate established Immulite 1000 diagnostic thresholds for plasma ACTH to three contemporary systems (Immulite 2000XPi, Tosoh AIA-900, and Tosoh AIA-360) using the Clinical Laboratory Standard...
Relationship between the estrus duration in cyclic mares and the endometrial gene expression on day 7 post-ovulation. This study investigated the effect of estrus duration on endometrial gene expression in cyclic mares on Day 7 post-ovulation, focusing on transcripts relevant to early pregnancy: uterocalin (P19), insulin-like growth factor 1 (IGF1), fibroblast growth factor 2 (FGF2), progesterone receptor (PGR), and estrogen receptor alpha (ESR1). Twelve mares were classified according to the estrus duration in long estrus (LE, ≥ 3 days of endometrial edema; n = 7) or short estrus (SE, 0.1). ESR1 expression was undetectable in all samples. These findings suggest that prolonged estrus enhances P19 e...
Effect of season of collection and storage method on equine hair cortisol concentration. Serum cortisol concentration is one of the common physiological reference standards for evaluating stress in animals. However, it only evaluates acute stress at the moment of blood collection. Hair cortisol concentrations (HCC) could provide a method for assessing cortisol concentrations over extended periods of time, giving an estimate of chronic stress levels. In this case, high HCC results could help equine managers alter management practices to improve welfare. Objective: To evaluate the effect of the month of collection and the storage method on equine HCC. Methods: Tail hair was collecte...
Adrenocorticotropic Hormone and Thyroxine Concentrations in Young Healthy Equids: Species Differences and Seasonal Variations. Due to growing interest in endocrine diseases, more studies aim to interpret the baseline concentrations and reference intervals of hormone values like adrenocorticotropic hormone (ACTH) and thyroxine (T4) in horses. Most studies available in the literature focus on evaluating ACTH and thyroid hormone values in adult and geriatric horses, with only a few considering younger donkeys and ponies. This study aimed to measure ACTH and T4 in autumn and spring in younger equids. The study included 42 young equids, which were divided into three groups: horses, ponies, and donkeys. The concentration of...
Multi-omics profiling of the testes in Kazakh horses across sexual maturation. Equus caballus is a species of considerable economic and cultural significance. However, the regulatory networks involved in equine sexual maturation remain unclear and eventually limit its reproduction and utilization. In this study, testicular tissues from eight Kazakh horses at two developmental stages (2 years, representing pre-maturation, and 3 years, representing post-maturation) were analyzed using whole transcriptome sequencing, data-independent acquisition (DIA) proteomics, and untargeted metabolomics. An integrated regulatory network was constructed encompassing ceRNA, mRNA, prot...
Temporal variation in incretin and insulin secretion in ponies in association with dietary macronutrients. Equine insulin dysregulation (ID) is a common condition that predisposes to hyperinsulinaemia-associated laminitis. Improved pathophysiological understanding would enable better management of ID and reduce the risk of laminitis. The incretin peptides, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), augment the insulin response to dietary glucose and GLP-1 has been implicated in the pathophysiology of ID. However, their temporal variation in response to a low-energy diet has not been reported. This study determined the variation in GLP-1, GIP and insulin ...
Relationship between the duration of endometrial edema and reproductive parameters of estrus, diestrus, and fertility in mares: a field study. The duration of endometrial edema has been positively correlated with uterine receptivity and likelihood of pregnancy. Therefore, this study aimed to evaluate whether there is a relationship between the duration of endometrial edema (DEdema) and other key parameters of the estrous cycle: maximum edema (MEdema), largest follicle diameter (LPF), corpus luteum and uterine tone on day 5 post ovulation (CLD5 and TD5), progesterone concentration (P4) and fertility. A total of 88 cycles from 36 mares were evaluated and divided into Short Estrus (SE), Long Estrus (LE), Inseminated (AI) and Non-insemin...
Assessment of baseline adrenocorticotropic hormone and insulin concentrations in healthy horses in Saskatchewan over a 1-year period. Endocrine disorders in horses, such as pituitary pars intermedia dysfunction and equine metabolic syndrome, rely on hormone testing for diagnosis, but seasonal and regional variabilities highlight the need for locally generated data. Objective: To characterize monthly blood concentrations of ACTH and insulin over 1 year in healthy horses in Saskatchewan. A secondary objective was to assess the association between these outcomes and the following factors: sex, age, breed, pregnancy status, level of exercise, body condition score, and cresty neck score. Methods: Sixty-eight clinically healthy, c...
Associations among beta-endorphin, ACTH, cortisol concentration, age, and clinical signs indicative of pituitary pars intermedia dysfunction in geriatric horses. Limited published data are available regarding the relationships among clinical signs associated with pituitary pars intermedia dysfunction (PPID), age, and concentrations of proopiomelanocortin-derived peptides and cortisol. Objective: Identify clinical signs associated with age, beta-endorphin (β-END), adrenocorticotropic hormone (ACTH), and cortisol concentrations and compare β-END and cortisol concentrations between horses with PPID and geriatric controls. Methods: A total of 113 horses aged 18-32 years. Methods: Cross-sectional study. Clinical signs were scored, plasma β-END, ACTH, an...
Effects of L-selenomethionine supplementation on nutrient digestibility and metabolism, antioxidant capacity, hormone levels, and fecal microbiota diversity in pregnant Yili mares during mid- to late gestation. L-selenomethionine (L-SeMet), a highly bioavailable organic form of selenium, plays a critical role in maintaining antioxidant homeostasis, regulating reproductive hormone secretion, and improving intestinal microbial ecology. Previous studies have demonstrated that appropriate supplementation with L-SeMet can significantly enhance the production performance and health status of ruminants. However, the nutritional regulatory mechanisms and physiological effects of L-SeMet in monogastric herbivores, particularly horses during mid- to late gestation, remain inadequately understood. Therefore, th...
Estrus synchronization and follicular development patterns in jennies. Seasonal variations and breed differences significantly influence reproductive efficiency in jennies, yet optimized, evidence-based estrus synchronization protocols for key Chinese breeds are lacking. Objective: This study aimed to compare the efficacy of three hormonal protocols on estrus synchronization, and to characterize follicular development patterns in DeZhou and Xinjiang jennies across different seasons. Methods: In two experiments (April-May, n = 94; July-August, n = 144), 238 non-pregnant jennies received one of three treatments: GnRH-PGFα with two injection timings (Treatment Grou...
Pancreatic islet remodeling in horses with hyperinsulinemia and pituitary dysfunction. The equine pancreas remains understudied, particularly in the context of endocrine disease. This study aimed to characterize regional islet distribution and composition in the normal equine pancreas and investigate how hyperinsulinemia (HI) and pituitary pars intermedia dysfunction (PPID) influence pancreatic islet morphology and hormone expression. In the first experiment, pancreas samples from eight healthy horses were collected and analyzed across three anatomical locations: left lobe, body, and right lobe. The left lobe exhibited a greater relative islet area and perimeter compared to the ...
Determining the timeline of gonadal and genital differentiation in male and female equine fetuses allows for early detection and intervention in malformations. Sexual differentiation in the equine fetus involves coordinated morphogenetic processes that shape both the gonads and the genital ducts. Although the formation of testes and ovaries has been relatively well documented, the temporal dynamics and morphometric patterns of the mesonephric (Wolffian) and paramesonephric (Müllerian) ducts remain insufficiently characterized. This study aimed to detail the timeline of gonadal and ductal differentiation in male and female equine fetuses during the critical developmental window between 60 and 80 days of gestation. Gross anatomical evaluation, histo...
GnRH Administration Increases Synchronisation of Ovulation in Mares. The objective of this study was to evaluate the effects of exogenous GnRH administration at the beginning of estrus synchronisation in mares during the spring transitional period. Estrus was synchronised using a progesterone releasing intravaginal device (PRID). The PRID was left in the vagina for 10 days, followed by an injection of 0.4 mg of cloprostenol at PRID removal. The GnRH group (n = 32) was subjected to intramuscular administration of 100 μg of the GnRH agonist triptorelin at PRID insertion, while the control group (n = 32) received 1 mL of sterile physiological sali...
Effects of total parenteral nutrition and electrolyte solutions with or without glutamine on the hormonal profiles of horses subjected to exploratory laparotomy. Starvation and nutritional support clinically influence horses, particularly during the treatment of gastrointestinal diseases and post-surgical recovery. In this study, we aimed to evaluate the effects of different nutritional strategies on the endocrine response of horses subjected to exploratory laparotomy followed by food deprivation. Sixteen healthy adult horses were randomly allocated into four groups (n=4) based on treatments: enteral fluid therapy without (ENTFL) or with glutamine (ENTGL), and parenteral fluid therapy with glucose (PARFL) or total parenteral nutrition with glutamine (P...
Effects of Social Interactions and Foundational Training on Behavior, Temperament, and Hormone Levels in Weanling Horses. Horses are social animals, with early life experiences playing a crucial role in their physiological and behavioral development. This study explored the influence of herd dynamics and foundational training on behavioral and hormonal changes in weaned foals. We examined 13 six-month-old Quarter Horse foals over a three-month training period, performing behavioral observations, temperament assessments, and hormone analyses at the start, midpoint, and end of the training. The results indicated that affiliative behaviors decreased significantly, while agonistic behaviors first increased and then d...
Seasonal effects on follicular dynamics and hemodynamics, ovarian hormone levels, nitric oxide levels, and lactate dehydrogenase levels in native mares. Summer heat stress affects the regularity of the estrous cycle in different animal species. Unassigned: This study aimed to investigate seasonal effects on follicular dynamics, hemodynamics, and associated biomarkers across the estrous cycle in native mares. Unassigned: Doppler ultrasound examinations and blood samples were collected along three sequential estrous cycles during the cold (November to March) and the hot months of the year (May to August). The diameter, antrum diameter, and color area of the dominant follicle (DF) were determined. The diameters, uterine horns, and corpus luteum (...
The ACTH ratio validates the thyrotropin-releasing hormone stimulation test to diagnose pituitary pars intermedia dysfunction but does not enhance performance. To evaluate the diagnostic performance of a post-/pre-thyrotropin-releasing hormone (TRH) plasma ACTH ratio for the diagnosis of pituitary pars intermedia dysfunction (PPID) in horses. Unassigned: This was a prospective, case-controlled study conducted monthly from January through December 2018 on 21 horses with PPID and 63 control horses. The ratios were calculated by dividing the plasma ACTH concentration obtained 30 minutes after IV injection of TRH by the pre-TRH plasma ACTH concentration. The effect of PPID and month were assessed using a linear mixed-effect model, and the diagnostic perf...
Equine oviduct-specific glycoprotein is modulated by hormones and sperm cells. Oviduct glycoprotein 1 (OVGP1) is a key protein involved in oviductal functions. β-estradiol (E) and progesterone (P), oxytocin (OXT) and tumor necrosis factor-α (TNFα) modulate the equine oviduct function, through prostaglandin regulation. The objective was to evaluate OVGP1 expression within each equine oviduct segment (infundibulum, ampulla isthmus), throughout the estrous cycle. The in vitro effect of (i) E, P, OXT, TNFα; and (ii) spermatozoa, on oviduct OVGP1 transcription and secretion was studied. Gene transcription was assessed by real-time PCR; protein expression by western blot; ...
Intra-articular methylprednisolone acetate does not induce hyperinsulinemia or hyperglycemia in metabolically normal horses. The goal of this project was to examine the metabolic effects of IA methylprednisolone acetate (MPA) following injection into multiple low-motion joints. Unassigned: Six 3-year-old geldings without pituitary pars intermedia dysfunction or insulin dysregulation were randomly injected with 20 mg of IA MPA/joint (80 mg total; bilateral distal hock joints) or an equal volume of saline. Serial blood samples were collected for resting ACTH, cortisol, insulin, and glucose, as well as insulin and glucose following repeated low-dose oral sugar tests. Treatments were crossed over after a 6-week washout,...
Progestagens Monitoring in 147 Mares in Order to Induce Foaling With Oxytocin. A total of 147 mares of different breeds (110 were sport or race horses, often very valuable) have been monitored over 5 years from 2012 to 2016. When at or near term, the mares were monitored in order to induce foaling, by checking the mammary development by palpation, analysing the colour and consistency of the precolostrum, estimating the calcium and antibodies concentrations in the precolostrum and by measuring the plasmatic progestagens concentration every day at 6 p.m. At the end of gestation, it has been observed that the progestagens rate levelled off (the top concentration varies from...
Pilot study of β-endorphin concentrations in horses with pituitary pars intermedia dysfunction using a newly validated enzyme-linked immunosorbent assay. β-endorphin, a proopiomelanocortin (POMC)-derived peptide secreted by pars intermedia melanotropes, may play a significant but underexplored role in pituitary pars intermedia dysfunction (PPID) pathophysiology and diagnosis. This study aimed to (1) validate a commercially available human β-endorphin enzyme-linked immunosorbent assay (ELISA) kit for equine samples, and (2) compare β-endorphin concentrations between horses with PPID and healthy controls. Assay validation included the generation of standard curves using purified synthetic equine β-endorphin and human β-endorphin standards, w...
