58 Awardee Talk: A decade of discovery in horse pasture utilization

Abstract Perennial cool-season grasses are the foundation of horse pastures in the North Central U.S. A majority of U.S. horses graze pastures as a way to encourage exercise and socialization, and to reduce feeding costs. However, other forages must be evaluated to help extend the grazing season and respond to emerging issues (e.g., floods and winter kill). This abstract summarizes the results of six individual grazing trials that aimed to evaluate forage yield, horse preference, forage nutritive value, and horse health parameters of perennial cool season grasses and alternative forages. Over 10 yr, multiple adult horses in good health grazed monocultures of perennial cool season grasses, annual cool season grasses, legumes, annual warm season grasses, and cover crops in replicated small plots designed in a randomized complete block. Yield was mechanically harvested, samples for forage nutritive value were hand harvested, and preference was visually assessed. Horses were allowed to rotationally graze forages using best management practices throughout multiple Minnesota growing seasons (May through October). Blood glucose and insulin concentrations were collected to determine the impact of certain forage species on horse health parameters. Data were analyzed using various procedures in SAS with P values ≤ 0.05. Forage yields varied greatly between forage types (P ≤ 0.05) and ranged from 13 to 2 Mgּ ha-1. Many forages that were higher yielding, were among the least preferred by horses, including orchardgrass, oat, alfalfa, sudangrass, radish, and turnip. The most preferred forages included Kentucky bluegrass, timothy, meadow fescue, annual ryegrass, winter wheat, red clover, white clover, teff, and berseem clover (P ≤ 0.05). Almost all forages had greater forage nutritive values that met or exceeded the nutritional needs of horses in maintenance. Many warm season grasses had inverted calcium to phosphorus ratios and increased nitrate-nitrogen content. While no consistent relationship was found, horse preference tended to be positively associated with crude protein and nonstructural carbohydrates. When evaluating health parameters, horses grazing teff, an annual warm season grass, had reduced average glucose, average insulin, and peak insulin compared with horses grazing perennial cool season grasses in the late fall (P ≤ 0.05). Collectively, these results suggest that strategic use of pasture forages can be used to help manage common horse health concerns (e.g., obesity and Equine Metabolic Syndrome). While perennial cool-season grasses will remain the foundation of horse pastures in the North Central U.S., this research identified other suitable forage alternatives. Placing a priority on the balance of forage yield and horse preference, annual ryegrass, alfalfa, teff, and berseem clover can be used as horse pasture forage alternatives to extend the grazing season, maximize yield, increase pasture nutritive value, help manage common horse health concerns, and when responding to emerging issues.