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BMC veterinary research2019; 15(1); 345; doi: 10.1186/s12917-019-2088-1

The effect of different grazing conditions on the insulin and incretin response to the oral glucose test in ponies.

Abstract: The oral glucose test (OGT) is a useful tool for diagnosing insulin dysregulation (ID) and is somewhat repeatable in ponies under consistent management. This study aimed to determine whether the insulin and incretin responses to an OGT in ponies differed after short-term access to fertilised pasture, compared to unfertilised pasture, by using a randomised, repeated measures study design. Sixteen mixed-breed ponies were classified as severely insulin-dysregulated (SD; post-prandial insulin ≥80 μIU/mL) or not severely insulin-dysregulated (NSD; post-prandial insulin < 80 μIU/mL) using an OGT prior to the study. The ponies accessed pasture that was fertilised, or unfertilised, for 5 days (4 h/day, with supplemental hay provided at 0.7% bodyweight), with a 10 day period between phases. An OGT was performed after each phase. Glucose, insulin, active glucagon-like peptide-1 (aGLP-1), and glucose-dependent insulinotropic polypeptide (GIP) were measured in post-prandial blood samples. Results: The volume of fertilised pasture was five-fold greater than unfertilised pasture, with % non-structural carbohydrates (NSC) similar between all forages. Consuming fertilised pasture increased (P = 0.018) the serum insulin response to an OGT, compared to grazing unfertilised pasture. A limitation of the study was that pasture intake was unable to be quantified. Insulin responses were greater in SD, compared to NSD, ponies (P < 0.001) and remained well above the test cut-off at all times. A subset of ponies, initially screened as NSD, became (more) insulin-dysregulated after pasture access. Further, aGLP-1 was a significant predictor of insulin concentration in this cohort. Conclusions: Whereas some insulin-dysregulated ponies were comparatively resistant to dietary intervention, others showed markedly different OGT responses following subtle changes in their forage-based diet. This implies that mild/early ID might be unmasked by dietary change, and that dietary management is important in these ponies. However, dietary management alone may not be adequate for all cases of ID.
Publication Date: 2019-10-16 PubMed ID: 31619223PubMed Central: PMC6794863DOI: 10.1186/s12917-019-2088-1Google Scholar: Lookup
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  • Journal Article

Summary

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The research investigates the impact of different grazing conditions (fertilised versus unfertilised pasture) on the insulin and incretin responses to an oral glucose test (OGT) in ponies. The researchers discovered that grazing on fertilised pastures leads to a higher insulin response compared to grazing on unfertilised pastures, emphasizing the importance of diet management in horses, particularly those at risk of insulin dysregulation.

Study Design

  • The researchers used a randomized, repeated measures study design to assess the effect of different grazing conditions on insulin regulation in ponies.
  • Sixteen mixed-breed ponies were classified as severely insulin-dysregulated (SD) or not severely insulin-dysregulated (NSD) using an OGT before the study.
  • The ponies grazed on either fertilised or unfertilised pasture for five days, with a 10 day period in between. An OGT was conducted after each phase.
  • Post-prandial blood samples were collected and analyzed for glucose, insulin, active glucagon-like peptide-1 (aGLP-1), and glucose-dependent insulinotropic polypeptide (GIP).

Results

  • The volume of fertilised pasture was five times greater than the unfertilised pasture, but the percentage of non-structural carbohydrates (NSC) was similar in both types of pastures.
  • Consuming fertilised pasture led to a significant increase in the insulin response to an OGT compared to grazing on unfertilised pasture.
  • Insulin responses were higher in SD ponies compared to NSD ones and stayed above the test cut-off at all times.
  • A subset of ponies initially classified as NSD became more insulin-dysregulated following pasture access, indicating that mild or early insulin dysregulation might be revealed by dietary changes.
  • aGLP-1 was a significant predictor of insulin concentration in the ponies.

Conclusions

  • The study shows that while some insulin-dysregulated ponies were relatively resistant to dietary intervention, others showed significant differences in their OGT responses following subtle changes in their forage-based diet.
  • The findings suggest that diet management is important for ponies, especially those at risk of insulin dysregulation.
  • However, diet management alone may not be enough in all cases, suggesting that comprehensive interventions may be needed for managing insulin dysregulation in ponies.
  • One of the study’s limitations was that the intake of the pasture by the ponies could not be precisely measured, which might impact the generalisability of the results.

Cite This Article

APA
Fitzgerald DM, Pollitt CC, Walsh DM, Sillence MN, de Laat MA. (2019). The effect of different grazing conditions on the insulin and incretin response to the oral glucose test in ponies. BMC Vet Res, 15(1), 345. https://doi.org/10.1186/s12917-019-2088-1

Publication

ISSN: 1746-6148
NlmUniqueID: 101249759
Country: England
Language: English
Volume: 15
Issue: 1
Pages: 345

Researcher Affiliations

Fitzgerald, Danielle M
  • School of Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, QLD, Australia.
Pollitt, Christopher C
  • School of Veterinary Science, University of Queensland, Gatton, QLD, Australia.
Walsh, Donald M
  • Animal Health Foundation, Pacific, MO, USA.
Sillence, Martin N
  • School of Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, QLD, Australia.
de Laat, Melody A
  • School of Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, QLD, Australia. melody.delaat@qut.edu.au.

MeSH Terms

  • Animal Feed / analysis
  • Animal Nutritional Physiological Phenomena
  • Animals
  • Cross-Over Studies
  • Diet / veterinary
  • Gastric Inhibitory Polypeptide / blood
  • Glucagon-Like Peptide 1 / blood
  • Glucose Tolerance Test / veterinary
  • Horse Diseases / metabolism
  • Horses
  • Hyperinsulinism / metabolism
  • Hyperinsulinism / veterinary
  • Incretins / blood
  • Insulin / blood
  • Metabolic Syndrome / veterinary
  • Peptide Fragments / blood
  • Queensland
  • Random Allocation

Grant Funding

  • NA / Animal Health Trust (US)

Conflict of Interest Statement

The authors declare that they have no competing interests.

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