A new study from The Ohio State University Agricultural Technical Institute suggests that to fully benefit from being on pasture, horses need room to roam. The data showed horses kept in pens that allowed 342 square meters (about one-tenth of an acre) per horse had reduced levels of blood cortisol, a hormone associated with stress.
Source: EQUUS, September 5, 2025. Link. The study focused only on the amount of space needed to reduce stress in a herd rather than to support grazing—two acres per horse is the generally accepted minimum to support healthy pasture growth and adequate nutritional intake.
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