Prevalence and risk factors for hyperinsulinaemia in ponies in Queensland, Australia

Objectives To determine the prevalence of hyperinsulinaemia in a population of ponies in Queensland, Australia, and identify associated factors. Methods Breeders or traders of ponies within a 100 km radius of Gatton, Queensland, were recruited for study using an internet database. Clinical and management details were obtained, including body condition score, fat deposition and history or evidence of laminitis. Blood samples were analysed for serum insulin and triglyceride concentrations and plasma adrenocorticotrophic hormone (ACTH) and leptin concentrations following short-term removal from pasture and withholding of supplementary food for at least 12 h. Results Of 23 pony studs identified, 22 were available for visit. The study population consisted of 208 ponies: 70 Australian Ponies; 67 Welsh Mountain Ponies or Cobs; 51 Connemara Ponies; 20 Shetland ponies. We excluded 20 with suspected pituitary pars intermedia dysfunction (>15 years, ACTH >50 pg/mL). In total, 27% of the ponies (51/188) were hyperinsulinaemic (insulin >20 mu IU/mL). The final multivariable model revealed increasing age, supplementary feeding and increased leptin and triglyceride concentrations to be associated with hyperinsulinaemia. Conclusions Hyperinsulinaemia was prevalent and associated with age and evidence of metabolic disturbance, including elevated leptin and triglyceride concentrations, in this population. A significant number of ponies were at risk of hyperinsulinaemia, which has implications for strategies to reduce the risk of laminitis in this population.