An ox (plural oxen), also known as a bullock in Australia and India, is a bovine trained as a draft animal or riding animal. Oxen are commonly castrated adult male cattle; castration makes the animals more docile. Cows (adult females) or bulls (intact males) may also be used in some areas. Oxen are used for plowing, for transport (pulling carts, hauling wagons and riding), for threshing grain by trampling, and for powering machines that grind grain or supply irrigation among other purposes. Oxen may be also used to skid logs in forests, particularly in low-impact, select-cut logging. Draft oxen are usually yoked in pairs. Light work such as carting household items on good roads may only require one pair, while for heavier work, further pairs would be added as necessary. A team used for a heavy load over difficult ground might exceed nine or ten pairs.