Dietary protein and(or) energy restriction in mares: plasma growth hormone, IGF-I, prolactin, cortisol, and thyroid hormone responses to feeding, glucose, and epinephrine.
Abstract: Sixteen light horse mares were fed diets of bermudagrass hay and a corn/cottonseed hull-based supplement formulated to contain either 100% (control) or 50% (restricted) of the protein and(or) energy requirements for maintenance in a 2 x 2 factorial arrangement of treatments. Plasma IGF-I, prolactin, cortisol, triiodothyronine, and thyroxine were monitored for 33 d. On the 27th d, frequent blood samples were drawn throughout the day for the measurement of growth hormone (GH), and on the 29th d, an epinephrine challenge and an i.v. glucose tolerance test (IVGTT) were performed in the morning and afternoon, respectively. Restriction of protein and(or) energy reduced (P < .001) plasma IGF-I concentrations within 24 h, and the effect persisted through the 24th d. Energy restriction decreased (P = .01) plasma cortisol concentrations, whereas thyroid hormones were not influenced (P > .1) by restriction of protein and(or) energy. Plasma prolactin concentrations were low throughout the experiment and after the IVGTT, but they increased (P = .003) after feeding. Protein restriction increased (P = .09) the occurrence of GH episodes during the 14-h feeding period on d 27; the greatest effect occurred in the mares restricted in both nutrients. In contrast, energy restriction reduced (P = .05) the GH response to epinephrine injection. We conclude that 1) protein deficiency in mares increases GH secretion, whereas energy restriction alone does not, 2) a deficiency in energy and(or) protein reduces IGF-I secretion, and 3) prolactin concentrations increase after feeding, even at a time of year when secretion rates are naturally low.
Publication Date: 1995-05-01 PubMed ID: 7665373DOI: 10.2527/1995.7351424xGoogle 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.
The research examines the impact of protein and/or energy restriction in light horse mares’ diet on several of their hormones such as growth hormone, IGF-I, prolactin, cortisol, and thyroid hormones. The study further investigates hormone responses to feeding, glucose, and epinephrine.
Study Procedure
- The experiment involved sixteen light horse mares who were fed different diets of bermudagrass hay and a corn/cottonseed hull-based supplement.
- The supplements were formulated to contain either 100% (control) or 50% (restricted) of the protein and/or energy requirements for them to maintain good health.
- This led to a 2 x 2 factorial arrangement of treatments.
- Various hormones were monitored for a period of 33 days.
- On the 27th and 29th days, they took frequent blood samples to measure growth hormone (GH) and then conducted an epinephrine challenge and an intravenous (i.v) glucose tolerance test.
Findings
- Protein and/or energy restriction reduced plasma IGF-I concentrations within 24 hours and this effect persisted through the 24th day of the experiment.
- Plasma cortisol concentrations decreased as a result of energy restriction, while thyroid hormones were not significantly influenced.
- Naturally low plasma prolactin concentrations were observed throughout the experiment and still low after the IVGTT, but levels increased after feeding.
- Protein restriction led to an increased occurrence of GH episodes during the feeding period on the 27th day, and the greatest effect was seen in the mares with both nutrients limited.
- Contrarily, the GH response to epinephrine injection was reduced when the diet was energy restricted.
Conclusion
- Protein deficiency in mares’ diet leads to an increase in GH secretion, but energy restriction alone does not cause any such increase.
- A deficiency in either or both energy and protein results in reduced IGF-I secretion.
- Additionally, prolactin concentrations increase after feeding, even when they are naturally low at that time of year.
Cite This Article
APA
Sticker LS, Thompson DL, Fernandez JM, Bunting LD, DePew CL.
(1995).
Dietary protein and(or) energy restriction in mares: plasma growth hormone, IGF-I, prolactin, cortisol, and thyroid hormone responses to feeding, glucose, and epinephrine.
J Anim Sci, 73(5), 1424-1432.
https://doi.org/10.2527/1995.7351424x Publication
Researcher Affiliations
- Department of Animal Science, Louisiana State University Agricultural Center, Baton Rouge 70803, USA.
MeSH Terms
- Animals
- Diet, Protein-Restricted / standards
- Diet, Protein-Restricted / veterinary
- Dietary Proteins / administration & dosage
- Eating / physiology
- Energy Intake / physiology
- Epinephrine / pharmacology
- Female
- Glucose / pharmacology
- Glucose Tolerance Test
- Growth Hormone / blood
- Horses / blood
- Horses / metabolism
- Hydrocortisone / blood
- Insulin-Like Growth Factor I / analysis
- Prolactin / blood
- Thyroid Hormones / blood
- Thyroxine / blood
- Triiodothyronine / blood
Citations
This article has been cited 7 times.- Ferreira C, Palhares MS, de Melo UP, Leme FOP, Maranhão RPA, Garcia HC, Gheller VA. Effects of total parenteral nutrition and electrolyte solutions with or without glutamine on the hormonal profiles of horses subjected to exploratory laparotomy. Braz J Vet Med 2026;48:e005725.
- Kim K, Melough MM, Kim D, Sakaki JR, Lee J, Choi K, Chun OK. Nutritional Adequacy and Diet Quality Are Associated with Standardized Height-for-Age among U.S. Children. Nutrients 2021 May 16;13(5).
- Connysson M, Rhodin M, Jansson A. Effects of Horse Housing System on Energy Balance during Post-Exercise Recovery. Animals (Basel) 2019 Nov 14;9(11).
- Niederecker KN, Larson JM, Kallenbach RL, Meyer AM. Effects of feeding stockpiled tall fescue versus summer-baled tall fescue-based hay to late gestation beef cows: I. Cow performance, maternal metabolic status, and fetal growth. J Anim Sci 2018 Nov 21;96(11):4618-4632.
- Vasconcelos AR, Cabral-Costa JV, Mazucanti CH, Scavone C, Kawamoto EM. The Role of Steroid Hormones in the Modulation of Neuroinflammation by Dietary Interventions. Front Endocrinol (Lausanne) 2016;7:9.
- Singh VK, Pattanaik AK, Goswami TK, Sharma K. Effect of Varying the Energy Density of Protein-adequate Diets on Nutrient Metabolism, Clinical Chemistry, Immune Response and Growth of Muzaffarnagari Lambs. Asian-Australas J Anim Sci 2013 Aug;26(8):1089-101.
- Lejeune JP, Franck T, Gangl M, Schneider N, Michaux C, Deby-Dupont G, Serteyn D. Plasma concentration of insulin-like growth factor I (IGF-I) in growing Ardenner horses suffering from juvenile digital degenerative osteoarthropathy. Vet Res Commun 2007 Feb;31(2):185-95.
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
