Omneity® Pellets
All-In-One Vitamin & Mineral Pellet
Association of season and pasture grazing with blood hormone and metabolite concentrations in horses with presumed pituitary pars intermedia dysfunction.
Abstract: Pituitary pars intermedia dysfunction (PPID) is a risk factor for pasture-associated laminitis, which follows a seasonal pattern. Objective: Hormonal responses to season differ between PPID and unaffected horses. Methods: Seventeen horses aged 8-30 years (14 horses ≥ 20 years of age). Methods: Longitudinal observational study. Blood was collected monthly from August 2007 until July 2008 after pasture grazing and again after overnight stall confinement. Blood hormone and metabolite concentrations were measured and pasture grass samples were analyzed to determine carbohydrate content. Analysis of variance analysis for repeated measures was performed. Results: Mean ACTH concentrations varied significantly over time (P < .001), with higher concentrations detected in August, September, and October compared with November-April. Pasture × time effects were detected for glucose and insulin concentrations, with peaks observed in September. Horses were retrospectively allocated to PPID (n = 8) and control (n = 9) groups on the basis of plasma ACTH concentrations. Changes in insulin concentrations over time differed in the PPID group when compared with the control group. Insulin concentrations were positively correlated with grass carbohydrate composition. Conclusions: PPID did not affect the timing or duration of the seasonal increase in ACTH concentrations, but higher values were detected in affected horses. Insulin concentrations differed between groups, but hyperinsulinemia was rarely detected. Glucose and insulin concentrations peaked in September when horses were grazing on pasture, which could be relevant to the seasonal pattern of laminitis.
Copyright © 2010 by the American College of Veterinary Internal Medicine.
Publication Date: 2010-07-28 PubMed ID: 20666984DOI: 10.1111/j.1939-1676.2010.0547.xGoogle Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
This research investigates the connection between season, pasture grazing and blood hormone and metabolite concentrations in horses that are assumed to have pituitary pars intermedia dysfunction (PPID), a condition which increases the risk of developing pasture-associated laminitis. The study finds that PPID does not impact the timing or length of the seasonal increase in ACTH hormone levels, but such levels were higher in affected horses. The highest insulin and glucose concentrations occurred in September when horses were grazing, relevant to the seasonal occurrence of laminitis.
Methods and Subjects
- The study performed was a longitudinal observational study with 17 horses ranging from 8 to 30 years of age, with most above 20 years old.
- Blood was collected monthly for a year, following grazing and after overnight stall confinement.
- The concentrations of the hormones and metabolites in the blood, as well as the carbohydrate content in the grass samples, were analyzed.
- An analysis of variance (ANOVA) was used for the repeated measures.
Results and Findings
- The ACTH hormone concentrations varied over time, with peak levels occurring in August, September, and October.
- Glucose and insulin concentrations showed variations due to the interaction of pasture and time, with peaks in September.
- The horses were retrospectively grouped into those with presumed PPID and others as control; differences were seen in insulin concentration changes over time between the two groups.
- Insulin concentrations were also seen to correlate positively with the carbohydrate composition of the grass.
Conclusions and Implications
- While PPID doesn’t affect the timing or duration of the ACTH hormone’s seasonal increase, affected horses were observed to have higher levels of the hormone.
- Insulin concentration changes over time were different between the control group and the PPID group.
- Hyperinsulinemia was rarely detected, despite differences in insulin concentrations between the groups.
- September showed a rise in glucose and insulin when horses were grazing – this could be indicative of the seasonal pattern of laminitis, which aligns with periods of increased grass intake.
Cite This Article
APA
Frank N, Elliott SB, Chameroy KA, Tóth F, Chumbler NS, McClamroch R.
(2010).
Association of season and pasture grazing with blood hormone and metabolite concentrations in horses with presumed pituitary pars intermedia dysfunction.
J Vet Intern Med, 24(5), 1167-1175.
https://doi.org/10.1111/j.1939-1676.2010.0547.x Publication
Researcher Affiliations
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA. nfrank@utk.edu
MeSH Terms
- Animal Husbandry
- Animals
- Body Weight
- Female
- Horse Diseases / blood
- Horses
- Hypothalamo-Hypophyseal System / physiology
- Male
- Pituitary Diseases / blood
- Pituitary Diseases / veterinary
- Pituitary Gland, Intermediate / pathology
- Pituitary-Adrenal System / physiology
- Seasons
- Time Factors
- Up-Regulation
Citations
This article has been cited 15 times.- Kirkwood NC, Hughes KJ, Stewart AJ. Prospective Case Series of Clinical Signs and Adrenocorticotrophin (ACTH) Concentrations in Seven Horses Transitioning to Pituitary Pars Intermedia Dysfunction (PPID). Vet Sci 2022 Oct 17;9(10).
- Kirkwood NC, Hughes KJ, Stewart AJ. Pituitary Pars Intermedia Dysfunction (PPID) in Horses. Vet Sci 2022 Oct 10;9(10).
- Thane K, Uricchio C, Frank N. Effect of early or late blood sampling on thyrotropin releasing hormone stimulation test results in horses. J Vet Intern Med 2022 Mar;36(2):770-777.
- Rossi G, Richardson A, Jamaludin H, Secombe C. Preanalytical variables affecting the measurement of serum paraoxonase-1 activity in horses. J Vet Diagn Invest 2021 Jan;33(1):59-66.
- Hu K, Stewart AJ, Yuen KY, Hinrichsen S, Dryburgh EL, Bertin FR. The effect of freeze-thaw cycles on determination of immunoreactive plasma adrenocorticotrophic hormone concentrations in horses. J Vet Intern Med 2020 May;34(3):1350-1356.
- Williams CA, Kenny LB, Burk AO. Effects of grazing system, season, and forage carbohydrates on glucose and insulin dynamics of the grazing horse. J Anim Sci 2019 May 30;97(6):2541-2554.
- Fitzgerald DM, Walsh DM, Sillence MN, Pollitt CC, de Laat MA. Insulin and incretin responses to grazing in insulin-dysregulated and healthy ponies. J Vet Intern Med 2019 Jan;33(1):225-232.
- Spelta CW. Equine pituitary pars intermedia dysfunction: current perspectives on diagnosis and management. Vet Med (Auckl) 2015;6:293-300.
- Secombe CJ, Tan RHH, Perara DI, Byrne DP, Watts SP, Wearn JG. The Effect of Geographic Location on Circannual Adrenocorticotropic Hormone Plasma Concentrations in Horses in Australia. J Vet Intern Med 2017 Sep;31(5):1533-1540.
- Frank N, Walsh DM. Repeatability of Oral Sugar Test Results, Glucagon-Like Peptide-1 Measurements, and Serum High-Molecular-Weight Adiponectin Concentrations in Horses. J Vet Intern Med 2017 Jul;31(4):1178-1187.
- Banse HE, Frank N, Kwong GP, McFarlane D. Relationship of oxidative stress in skeletal muscle with obesity and obesity-associated hyperinsulinemia in horses. Can J Vet Res 2015 Oct;79(4):329-38.
- Selim S, Elo K, Jaakkola S, Karikoski N, Boston R, Reilas T, Särkijärvi S, Saastamoinen M, Kokkonen T. Relationships among Body Condition, Insulin Resistance and Subcutaneous Adipose Tissue Gene Expression during the Grazing Season in Mares. PLoS One 2015;10(5):e0125968.
- Goodrich EL, Llanos-Soto SG, Ivanek R, Pinn-Woodcock T, Frye E, Wells A, Purdy SR, Berryhill E, Place NJ. Both Season and Equid Type Affect Endogenous Adrenocorticotropic Hormone Concentrations in Healthy Donkeys, Mules and Hinnies in the United States. Animals (Basel) 2026 Jan 16;16(2).
- Lopes A, Huber L, Durham AE. The Seasonality of Serum Insulin Concentrations in Equids and the Association With Breed, Age, and Sex. J Vet Intern Med 2025 May-Jun;39(3):e70089.
- Viviani P, Lavado RA, Chavarria NH, Ragno VM, Montgomery JB. Spring and fall blood concentrations of adrenocorticotropic hormone, insulin, and thyroxine in healthy horses in Saskatchewan. Can Vet J 2024 Apr;65(4):335-342.
Use Nutrition Calculator
Check if your horse's diet meets their nutrition requirements with our easy-to-use tool Check your horse's diet with our easy-to-use tool
Talk to a Nutritionist
Discuss your horse's feeding plan with our experts over a free phone consultation Discuss your horse's diet over a phone consultation
Submit Diet Evaluation
Get a customized feeding plan for your horse formulated by our equine nutritionists Get a custom feeding plan formulated by our nutritionists
