Interstitial glucose concentrations over time in horses fed sweet feed or a low-moisture, molasses-based block supplement1

This preliminary study compares the effects of a twice-daily meal of sweet feed (SF) to a free-choice molasses-based block (BL) on interstitial glucose patterns in horses. Six geldings were equipped with continuous glucose monitoring systems and used in a crossover design over two 6-d periods. Diets consisted of free-choice prairie hay with either SF fed twice daily or free-choice access to a BL. Total intake was not different, with 10.6 kg of DM for horses on both dietary treatments (P > 0.05). A novelty effect was observed where horses consumed more BL in the first 12 h of exposure than during any remaining time period. Mean interstitial glucose concentration was 3.55 ± 0.15 and 4.18 ± 0.13 mM for horses consuming SF and BL, respectively (P = 0.44). Horses consuming SF had an initial glucose response that ranged from immediate to 2 h, and there was a second significant glucose response in 1 to 2 horses per time period that ranged from 2 to 4 h after feeding. The amount of BL consumed was significantly positively correlated with glucose response in 3 of 4 horses over multiple time periods (P ≤ 0.05). The maximum correlation between BL consumed and glucose response was r = 0.25 for 2 horses and r = 0.42 for the third horse. Patterns of postprandial glucose response varied from an immediate effect, to a delay of 15 min, to a delay of 4.5 h (P ≤ 0.05). Glucose responses were similar between treatments, although variability among horses was noted in quantity of BL consumed as well as timing and magnitude of glucose responses.