148  Analysis of purported insulin modulators on glycemic and insulinemic responses to various feeds in mature horses

Abstract

Understanding the insulinemic and glycemic responses to common equine feeds and the efficacy of purported insulin modulators, such as aloe vera and grape seed extract, is valuable in designing appropriate equine diets. Using a repeated 5 × 5 Latin square design, dehydrated alfalfa (DA), beet pulp (BP), oats (O), steam-flaked corn (C), and steam-flaked corn with an insulin modulator consisting of combined aloe vera and grape seed extract (CIM) were tested for glycemic and insulinemic response in 10 mature horses aged 6 to 25 years with an average of 11.5 years. The various feeds were fed at the rate of 1.5 g/kg of body weight on an as-fed basis. The aloe vera and grape seed extract were fed at the rates of 150 mg/kg and 20 mg/kg of body weight respectively. Horses were maintained on a forage-only diet consisting of pasture grazing and hay, except once per week, when they were stalled and subjected to a glycemic response test. For testing, hay was removed the evening before, and a 12-h fasted blood sample was taken at time 0 before providing the assigned treatments. Horses were allowed 30 min to consume each treatment before any ORTS were removed. Additional blood samples were taken via jugular catheter at 30, 60, 90, 120, 150, and 180 min post-feeding. Blood glycemic and insulinemic responses were evaluated by maximum concentrations and time to peak response (minutes). Peak glucose and insulin were determined by Proc Mixed function in SAS 9.4 with the main effect of treatment and the random variables of horse and week. Results are presented as lsmeans ± SEM. Both DA and BP had lower peak glucose and insulin concentrations (P < 0.05) than the 3 high starch concentrate treatments (O, C, and CIM). The addition of insulin modulators to steam-flaked corn had no effect on the response for peak glucose [C: 128 ± 5 mg/dL, CIM: 133 ± 5 mg/dL, P = 0.39] or insulin [C: 54.5 ± 15.6 µIU/mL, CIM: 58.6 ± 15.6 µIU/mL; P = 0.78]. Likewise, the addition of the insulin modulators did not impact time to peak glucose concentrations [C: 93 ± 9 min, CIM: 108 ± 9 min, P = 0.23], nor the time to peak insulin concentrations [C: 81 ± 13 min, CIM: 87 ± 13 min, P = 0.73]. The results support that feeds with greater starch concentrations produce higher maximal blood glucose and insulin concentrations, but that, in this study, the addition of insulin modulators to steam-flaked corn did not result in a detectable change in the horses’ insulinemic and glycemic response.