Andrew van Eps

Background Horseshoes with modified contact surfaces combined with deformable ground substrates are used to change hoof orientation during mid‐stance, for example, for therapeutic reasons. Objectives To measure the effect of horseshoes and ground substrates on sagittal and transverse plane hoof orientation at mid‐stance using a dorsal hoof wall mounted triaxial accelerometer. Study design In vivo experiment, randomised crossover design. Methods Differences in sagittal and transverse plane angles between standing and mid‐stance of the left front hoof of six horses walking with regular horseshoes, egg bar, toe‐wide, medial‐wide, lateral‐wide and three‐degree egg bar shoes on turf, sand and hard ground substrates were assessed with linear mixed models with horseshoe and substrate type as fixed factors ( p < 0.05) for each animal. Results Hoof angles were significantly affected by horseshoe ( p < 0.001), surface ( p < 0.001) and the combination ( p < 0.001). The sagittal plane angle increased in deformable ground substrates at walk‐in mid‐stance on turf [mean (±standard deviation): 2.6° (±3.8°)] and on sand [2.6° (±4.1°)] across all shoes. The greatest increase was observed with egg bar shoes [turf: 4.37° (±3.82°); sand 4.69° (±3.83°)]. There was a tendency for the hoof to sink laterally into deformable ground substrates among all shoes [turf: 1.11° (±1.49°); sand: 0.93° (±1.93°)]. Medial‐wide shoes increased the lateral sinking [turf: 2.00° (±1.63°); sand: 1.79° (±1.58°)]. Lateral‐wide shoes reduced the lateral sinking on turf [0.62° (±1.26°)] and induced a marginal medial sinking on sand [−0.007° (±2.03°)]. Main limitations The substrate properties were not quantitatively assessed, and observations were limited to front hooves at the walk. A larger sample size would be preferable. Conclusions Mid‐stance hoof orientation changes with specific combinations of shoes and ground substrates in the walking horse.

Background A single dose of metformin administered 1 h prior to oral glucose challenge was previously shown to reduce insulinaemic responses in horses with experimentally‐induced insulin dysregulation (ID). Targeted administration could be useful for controlling post‐prandial hyperinsulinaemia in horses with naturally‐occurring ID. Objectives The objective was to compare the insulinaemic and glycaemic responses to oral sugar testing (OST) performed at different intervals after a single dose of metformin in horses with naturally‐occurring ID. We hypothesised that pre‐treatment with one dose of metformin would significantly decrease the insulinaemic response to OST. Study design Randomised cross‐over in vivo experiment. Methods Eight university‐owned adult horses with naturally‐occurring ID underwent OST 1, 2 and 6 h following a single oral dose of metformin (30 mg/kg) or 1 h after placebo (240 mL water) with a 7‐day washout between treatments over a period of 3 weeks. Plasma insulin, C‐peptide and glucose concentrations were measured at 0, 60 and 90 min after 0.45 mL/kg light corn syrup and the effect of treatment (and the interval since dosing) examined using a mixed effects linear regression model. Results Metformin treatment had no significant effect on plasma glucose, insulin or C‐peptide concentrations at any time point compared with placebo ( p > 0.05). For OST 1 h post metformin, median (IQR) plasma insulin was 91.3 (62.4–114.9) μIU/mL at 60 min versus 76.2 (59.1–134.5) for placebo ( p = 0.8) and 62.7 (31.4–109.7) at 90 min versus 51.8 (29.2–126.3) for placebo ( p = 0.9). Main limitations Small sample size may limit identification of more subtle decreases in insulin concentration with metformin pre‐dosing. The results of this study are relevant only for one pre‐treatment dose (30 mg/kg) which limits extrapolation to predictions about the effects of longer‐term metformin administration on insulin and glucose dynamics in the horse. Conclusions and clinical importance The results do not support the use of targeted metformin treatment to reduce post‐prandial hyperinsulinaemia in horses with naturally‐occurring ID.