Graduate Research Assistant M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky Rockfield, KY, United States
Abstract:
Background: Restricted pasture intake is often recommended for horses at risk of laminitis but more information on the effect of changes in pasture water soluble carbohydrate (WSC) content on blood parameters in grazing insulin dysregulated (ID) equids is required. Hypothesis/
Objectives: To examine changes in pasture nutrient content and corresponding serum insulin concentrations in ID and non-ID (NID) horses over a 24-hour early fall grazing period.Animals: Twelve adult horses (Mean±SD; age 19.0±3.04yrs) were classified as ID (n=6) and NID (n=6) by history and diagnostic testing, using basal insulin and oral sugar tests.
Methods: Horses were group housed on pasture with ad libitum access to forage and water. Peripheral blood and pasture samples were collected every 2 hours for a 24-hour period. Serum was analyzed for insulin (AIA) and cortisol (RIA) concentrations, and whole blood glucose (glucometer). Pasture samples were analyzed for crude protein, WSC, ethanol soluble sugars, and starch (Equi-analytical). Two-way RM ANOVA (Prism) was used.
Results: A change in pasture WSC from 8.3% to 11.6%, between baseline 0700hrs and 1500hrs, respectively, was correlated with a significant increase (P=0.02) in insulin (delta mean±SD; 86.04±14.76µIU/mL) in ID horses but no change in NID horses. Glucose changed overtime in both groups. Cortisol showed the same circadian changes in ID and NID horses.Conclusions and clinical importance: Relatively small changes in pasture WSC can lead to significant increases in serum insulin in ID but not NID horses. Time of access should be closely monitored when allowing ID horses to graze.
