The repeatability of an oral glucose test in ponies.

Abstract

REASONS FOR PERFORMING STUDY: Insulin dysregulation can be difficult to diagnose from basal insulin and glucose concentrations, so a field-based oral glucose test (OGT) is preferred. However, the repeatability of this test has not been reported. OBJECTIVES: To determine the repeatability of an in-feed OGT in ponies and examine some factors affecting the palatability of the test meal. STUDY DESIGN: A repeated measures, longitudinal study. METHODS: An in-feed OGT was performed at 08.00 h on 3 consecutive occasions under controlled conditions in 8 mixed breed ponies. d-glucose (0.75 g/kg bwt) was dissolved in water and combined with wheat bran and lucerne chaff. Blood samples were taken before and 90, 120, 180 min and 24 h after d-glucose. The repeatability of the test was analysed with repeated measures ANOVA. Insulin and glucose responses to d-glucose were also compared to an equivalent dose of dietary carbohydrate provided with a commercial grain mixture. RESULTS: The overall insulin responses to the OGTs did not differ between tests. Individual insulin responses were more variable (P<0.05) than glucose responses. There was no difference in insulin concentration in post d-glucose samples over time. Insulin and glucose responses to grain and d-Glucose were not different. CONCLUSIONS: An OGT is reasonably repeatable in ponies. The currently recommended post-glucose sampling time point of 2 h is acceptable, with sampling at 90 min also likely to produce a consistent result. The use of an alternative carbohydrate source to d-glucose, such as a commercial grain-based product, may be a viable and more palatable option for the test.