At the 2023 AAEP Convention, Allison Palmer, DVM, of the Ohio State University College of Veterinary Medicine, discussed dietary protein’s influence on postprandial insulin levels. Previous recommendations for feeding horses with insulin dysregulation (ID) include low-nonstructural-carbohydrate (NSC) forage as well as low-NSC/high-protein ration balancers. High-protein meals, however, appear to be associated with an exacerbated insulin response in insulin dysregulated horses. In her review, Palmer reported:
- A ninefold greater insulin response in ID horses following a 31% crude high-protein meal (4 g/kg) when compared to normal horses.
- Following experimentally induced insulin dysregulation, horses displayed significantly higher glycemic and insulinemic response to high-protein meals (32% crude protein, 1 kg) compared to baseline.
This is significant because specific amino acids (arginine and leucine, for example) are robust activators that target rapamycin (mTOR) signaling at both the tissue level and systemically. The mTOR pathway activates a broad array of anabolic functions in response to nutrient ingestion, resulting in cell and tissue growth, energy storage, and protein synthesis. However, prolonged mTOR activation results in insulin resistance and associated changes within digital lamellae, such as decreased epithelial polarity and basement membrane adhesion. mTOR signaling has been demonstrated within digital lamellae in horses with all three forms of equine laminitis: sepsis-related, hyperinsulinemia-associated, and support-limb.
Palmer concluded that high-protein ration balancers might exacerbate insulinemic responses in horses with insulin dysregulation. In general, dietary protein ingested in excess of nutritional requirements over time has negative effects on systemic insulin and glucose dynamics. Products with lower protein content of no more than 12-15% crude protein might be better options to reduce the risk of exacerbating hyperinsulinemia in insulin dysregulated horses.
