TABLE 5.
Insulin parameters of oral glucose tolerance tests (OGTTs) performed in Shetland pony mares on a control or high‐energy (HE; 200% of energy requirements) diet for 24 weeks (2014), 17 weeks hay‐only (winter break 2014‐2015), and another 29 weeks control or HE diet (2015)
| Median basal plasma insulin concentration (mU/L) (range) | Median peak plasma insulin concentration (mU/L) (range) | Median time of peak insulin concentration (min) (range) | Median area under the curve for insulin (mU/L × min) (range) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Year 1 (RIA) | Dietary period | Control | HE | Control | HE | Control | HE | Control | HE |
| OGTT 0 | 0 | 1 (0) | 1 (0) | 25.5 (4.9‐30) | 34 (10‐84) | 90 (60‐120) | 120 (90‐120) | 1822 (405‐2013) | 2310 (577‐5835) |
| OGTT 1 | 1 | 1 (1‐8.3) | 1 (1‐8.4) | 17.5 (14‐134) | 39 (12‐205) | 90 (90) | 90 (60‐120) | 1448 (1122‐8239) | 3300 (699‐16 746) |
| OGTT 2 | 2 | 1 (0) | 1 (1‐4.8) | 16 (10‐21)a | 64 (21‐248)b | 120 (90‐120) | 90 (60‐120) | 1405 (756‐1950) | 4590 (2040‐17 847) |
| OGTT 3 | 3 | 1 (0) | 2.5 (1‐7.4) | 11.5 (8.7‐15)c | 51 (15‐283)d | 120 (90‐120) | 90 (30‐120) | 857 (772‐1320)o | 3690 (1860‐23 556)p |
| OGTT 4 | 4 | 1 (0) | 3.7 (1‐10) | 10.2 (8.8‐26)e | 70 (10‐332)f | 120 (90‐120) | 90 (30‐120) | 816 (606‐2265)q | 5595 (778‐26 854)r |
| Year 2 (CLIA) | |||||||||
| OGTT 0 | 5 | 2 (0) | 2 (0) | 13.8 (7.7‐39) | 21.7 (18.6‐61.3) | 120 (120) | 120 (120) | 820 (439‐2916) | 1372 (960‐3405) |
| OGTT 1 | 6 | 2 (0) | 2 (0) | 16.2 (7.1‐37.2)g | 94.7 (36.9‐157)h | 120 (120) | 105 (90‐120) | 1103 (376‐3264)u | 7177 (2805‐9975)v |
| OGTT 2 | 7 | 2 (0) | 2.1 (2‐4.7) | 11.0 (2‐27.8)i | 153.4 (55.5‐283)j | 120 (120) | 105 (90‐120) | 858 (240‐2160)u | 12 247 (5505‐21 630)v |
| OGTT 3 | 8 | 2 (0) | 2.5 (2‐6.9) | 7.7 (2‐8.4)k | 140.4 (51.6‐262)l | 120 (120) | 75 (60‐120) | 495 (240‐586)u | 10 147 (4320‐20 175)v |
Note: 2014:4 control, 7 HE ponies (period 2, n = 5 HE); 2015:6 control, 4 HE ponies (period 8, n = 3 control). Different superscripts within the same row indicate significance ab P = .02; cd P = .01; ef P = .04; gh P = .02; ij P = .01; kl P = .03; op P = .008; qr P = .007; uv P = <.001.