Horses do not rip the roots out of grass while eating. They use their strong, flat teeth to tear off grass blades close to the ground without pulling or digging into the soil.
Grass roots are typically deep and sturdy, making them difficult for a horse to uproot. Allowing roots to remain intact is also important for pasture health, as it lets grass regrow after grazing.
Horses can still affect the soil through hoof compaction, especially in wet conditions, and overgrazing can eventually damage root systems if pasture is eaten down too far. Overall, however, horses are designed to graze without destroying grass roots.