The effect of age and diet on the oral glucose tolerance test in ponies.

To evaluate the effects of age and diet on the oral glucose tolerance test (OGTT) in healthy ponies, OGTTs were performed on 2 groups of British native breed ponies (Group A: 7 foals [6-9 months], Group B: 7 mature individuals [6-13 years]) when maintained on either a high fibre pelleted ration only (Groups A and B) or a hay only diet (Group B). Plasma glucose response, following oral glucose administration, for Group A (basal plasma glucose concentration [Glu0] 4.6 +/- 0.4 mmol/l (mean +/- s.d.) increasing to 11.5 +/- 1.3 mmol/l at 90 min) was significantly different (P < 0.05) from that observed for Group B (Glu0 of 4.3 +/- 0.2 mmol/l increasing to 6.8 +/- 1.3 mmol/l at 90 min), when fed the same diet. For Group B ponies, the plasma glucose response, following oral glucose administration, was significantly different (P < 0.05) when fed hay only (Glu0 4.6 +/- 0.4 mmol/l increasing to 9.6 +/- 2.1 mmol/l at 150 min) compared to when fed the high fibre pelleted ration. These results indicate that both age and diet have a significant effect on plasma glucose concentrations measured during an OGTT.