Effects of pasture consumption and obesity on insulin dysregulation and adiponectin concentrations in UK native-breed ponies

Barnabé, MA; Elliott, J; Harris, PA; Menzies-Gow, NJ

Abstract

Background Insulin dysregulation (ID) and hypoadiponectinaemia (total [adiponectin] <7.9 mu g/mL) are risk factors for laminitis. They are sometimes, but not always, associated with obesity. Objectives To investigate the effects of pasture consumption and obesity on ID and circulating total [adiponectin] in ponies. Study Design Longitudinal. Methods Seven native-breed ponies with normal basal and post-oral sugar test (OST) [insulin] and body condition score (BCS) 4.3-5.5/9 were allowed to graze until they reached BCS 7/9. Ponies were then maintained at BCS 7/9 until completion of the study (week 22). Morphometric measures, OST, insulin tolerance test (ITT), plasma [adiponectin], whole-blood expression of receptors for adiponectin, insulin, and insulin-like growth factor 1, and pasture conditions (height and vigour) were determined fortnightly. Results Median (range) BCS increased significantly (p < 0.001) from 5.0 (4.3-5.5; week 0) to 7.2 (5.7-7.5; week 22). Basal [insulin] did not change significantly over the study, but median post-OST [insulin] was significantly higher (p < 0.05) at week 14 (95.2 [17.9-114.0] mu IU/mL), week 16 (103.0 [16.4-166.0] mu IU/mL), and week 20 (93.6 [10.0-153.0] mu IU/mL) than week 0 (25.0 [10.0-64.0] mu IU/mL). Compared with week 0, ITT results were significantly lower at weeks 2-6 and 12-20, and [adiponectin] was significantly lower at weeks 10-22 (p < 0.05). [Adiponectin] decreased in all ponies during the study. Both low (3/10) and high (8-9/10) pasture scores were significantly associated with low ITT results. Low pasture scores were associated with low [adiponectin]. BCS was significantly associated with basal [insulin], post-OST [insulin], ITT results, but not [adiponectin]. Main Limitations No control group with maintenance of ideal BCS; small sample size comprising native UK ponies. Conclusions Six ponies developed hypoadiponectinaemia, and all showed transient or consistent ID during the study. Both short, stressed grass and long, lush grass were associated with decreased tissue insulin sensitivity.

Citation

Barnabé, M., Elliott, J., Harris, P., & Menzies-Gow, N. (2025). Effects of pasture consumption and obesity on insulin dysregulation and adiponectin concentrations in UK native-breed ponies. Equine Veterinary Journal, https://doi.org/10.1111/evj.14507

• Journal Article Type: Article
• Acceptance Date: Mar 20, 2025
• Online Publication Date: Apr 21, 2025
• Publication Date: 2025
• Deposit Date: May 15, 2025
• Publicly Available Date: May 15, 2025
• Print ISSN: 0425-1644
• Electronic ISSN: 2042-3306
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• DOI: https://doi.org/10.1111/evj.14507
• Keywords: adiponectin; body condition score; equine metabolic syndrome; horse; insulin dysregulation; laminitis; pony; MOLECULAR-WEIGHT ADIPONECTIN; ADIPOKINE CONCENTRATIONS; INCREASED ADIPOSITY; BODY CONDITION; FAT; HORSES; SENSITIVITY; TISSUE