Postprandial Blood Glucose and Insulin Responses of Horses to Feeds Differing in Soluble Fiber Concentration

Insulin dysregulated horses metabolic responses to forage pellets

Hyperinsulinemia-associated laminitis (HAL) is the primary concern for insulin dysregulated (ID) equids and their insulin response to the consumption of oral, nonstructural carbohydrates (NSC) has been shown to be a risk predictor for HAL development. This randomized, crossover study's objective was to examine the insulinemic responses to 3 forage pellets (1 g/kg BW) (timothy hay, TH, 9.5 % CP & 10 % NSC DM; alfalfa hay, AH, 16.3 % CP & 9.8 % NSC DM; timothy-alfalfa hay; TAH, 17.2 % CP & 9.8 % NSC DM) along with a positive (dehulled oats; OG, 14.7 % CP & 59.7 % NSC DM) and negative dietary challenge control (low-NSC; LNSC, 12.8 % CP & 5.4 % NSC DM) of ID (n = 8; 16.1 ± 2.2 yr; 565.4 ± 99.1 kgs.) and non-ID (NID; n = 7; 17.0 ± 2.8 yr; 583.6 ± 57.9 kgs.) horses. ID horses had higher positive incremental area under the curve for insulin (IAUCi) (ID: 890 ± 925 µIU/mL*minute vs. NID: 225 ± 228 µIU/mL*minute), peak (ID: 101.5 ± 80.72 µIU/mL vs. NID: 25.7 ± 7.2 µIU/mL), and delta (ID: 45.5 ± 77.1 µIU/mL vs. NID: 4.9 ± 5.3 µIU/mL) insulin for all forage pellets compared to NID (p < 0.01). ID horses IAUCi for the forage pellets was not different compared to the LNSC (218 ± 327 µIU/mL*minute) but was different from OG (10,522 ± 4,565 µIU/mL*minute). ID horses' lack of an augmented insulinemic response to the low NSC forage pellets (fed in small amounts) indicates that they could be a safe feedstuff for ID animals.

Effects of Differences in Fibre Composition and Maturity of Forage-Based Diets on the Fluid Balance, Water-Holding Capacity and Viscosity in Equine Caecum and Colon Digesta

Horses are herbivores, and their hindgut functions as a fluid reservoir as forage fibre properties have great impact on the water content of digesta and the milieu in the ecosystem. Our objective was to compare the effect of grass fibre maturity and legume forage on the water-holding capacity (WHC) and viscosity of the equine hindgut and the body weight (BW) and fluid balance of horses. Three diets: concentrate and late harvested grass haylage (35:65 energy ratio) (C); early and late harvested grass haylage (80:20) (G); lucerne and late harvested grass haylage (80:20) (L) were fed to six caecum and colon fistulated horses for 28 days in a Latin-square design. Total water intake and BW were higher when the horses were fed Diet L, but the digesta WHC was higher when fed Diet G. Total water excretion (via faeces + urine) and the difference in total water intake-output was higher when fed Diet L. Viscosity, measured on centrifuged digesta fluid, did not differ between diets, but the individual colon data of one horse were higher. In conclusion, early harvested forage might be beneficial for the fluid balance of athletic horses providing a higher WHC of hindgut digesta without increasing BW. The importance of digesta viscosity in relation to equine diets needs further investigations.