From the January 2019 Issue of the University of Minnesota Extension – Horse Newsletter….

Research Update: Evaluating Glucose and Insulin Levels in Grazing Horses

By: Michelle Deboer, PhD, University of Wisconsin – River Falls, Marcia Hathaway, PhD, University of Minnesota, Craig Sheaffer, PhD, University of Minnesota, Kerry Kuhle, DVM, University of Minnesota, Krishona Martinson, PhD, University of Minnesota, and Patty Weber, PhD, Michigan State University

Photo Credit: Michelle Deboer, PhD, University of Wisconsin – River Falls

Forage is a primary part of the horse’s diet and is often fed in the form of cool-season grasses, legumes or warm-season grasses. These forage types differ widely in their nutritional content. Two main differences are the nonstructural carbohydrates (NSC) and fiber content. Therefore, the goal of this research, conducted at the University of Minnesota, was to explore the nutrient values of the forages and their effects on horses.

Six aged horses were grazed on cool-season grass, legume and warm-season grass pastures. Horses grazed legume and cool-season grass in the spring, all three forages in the summer and fall, and cool-season and warm-season grass in the late fall. Forage availability during each season was impacted by the Minnesota climate. During each season forage and blood samples were taken before turning out the horses and again two, four, six, and eight hours following turnout. In addition, the nutrient content of each forage and the glucose and insulin levels in the blood samples were determined.

The forage types each differed in nutrient content during the grazing period. Legume and cool-season grasses had a higher digestible energy (DE) compared to warm-season grass. Warm-season grass had lower NSC compared to cool-season grass in the summer and late fall. The fiber levels were highest in warm-season grass compared to the other forage types. Horses grazing warm-season grass had a lower average glucose and insulin content in the late fall and a lower peak insulin content in the fall and late fall when compared to horses grazing cool-season grass.

While glucose and insulin values were not different in the spring and summer, glucose and insulin values were lower for horses grazing warm-season grass in the fall and late fall compared to horses grazing cool-season grasses. As a result, the lower NSC and higher fiber values of warm-season grass could help decrease the insulin response of horses grazing in the fall and late fall. To learn more about this research, click here.

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