Grazing cattle or goats in rotation with horses can be beneficial if you have the time and resources to manage the process.
A handful of horses graze in a pasture one week; a herd of goats mow down its bushes and weeds the next. This multi-species rotational grazing system has its advantages, but whether they outweigh the disadvantages will depend on your situation, purposes, climate, and forage growth.
Advantages of grazing multiple species on land over grazing horses alone include more efficient plant use, better weed and brush control, improved natural parasite control, and more income per acre if you farm for a living and can accommodate more animals on your pastures. Disadvantages include possible disease transmission from one species to another and the need for more facilities, labor, and management.
In nature animals roam wild, and herds of horses or zebras travel long distances and eat native grasses, complementing the grazing behavior of bison, wild cattle, wildebeest, elk, etc., that eat grasses and forbs (any herb that is not a grass). They also share the ecosystem with ruminants such as deer, antelope, wild goats, and other animals that browse and prefer shrubs and forbs to grass.
Horses are selective grazers, overgrazing their favorite areas of a pasture while leaving other plants to grow tall. This creates roughs (piles of manure) and lawns (uncontaminated areas). If you add another species that prefers different plants, you can overcome the problem of inefficient forage use. Keep in mind, however, that if a pasture is already overgrazed, multiple species might do