Title: Bull
Content:   Many cattle ranches and stations run bulls with cows, and most dairy or beef farms traditionally had at least one, if not several, bulls for purposes of herd maintenance. However, the problems associated with handling a bull (particularly where cows must be removed from his presence to be worked) has prompted many dairy farmers to restrict themselves to artificial insemination (AI) of the cows. Semen is removed from the bulls and stored in canisters of liquid nitrogen, where it is kept until it can be sold, at which time it can be very profitable; in fact, many ranchers keep bulls specifically for this purpose. AI is also used to improve the quality of a herd, or to introduce an outcross of bloodlines. Some ranchers prefer to use AI to allow them to breed to several different bulls in a season or to breed their best stock to a higher-quality bull than they could afford to purchase outright. AI may also be used in conjunction with embryo transfer to allow cattle producers to add new breeding to their herds.
Title: Bull
Content:  and is brought up short. Alternatively, the bull may be hobbled, or chained by his ring or by a collar to a solid object such as a ring fixed into the ground. In larger pastures, particularly where a bull is kept with other cattle, the animals may simply be fed from a pickup truck or tractor, the vehicle itself providing some protection for the humans involved. Generally, bulls kept with cows tend to be less aggressive than those kept alone. In herd situations, cows with young calves are often more dangerous to humans. In the off season, multiple bulls may be kept together in a "bachelor herd".
Title: Bull
Content:   A bull is an intact (i.e., not castrated) adult male of the species Bos taurus. More muscular and aggressive than the females of the same species, the cows, bulls have long been an important symbol in many cultures, and play a significant role in beef ranching, dairy farming, and a variety of other cultural activities, including bullfighting and bull riding.
Title: Dairy cattle
Content:  A bull calf with high genetic potential may be reared for breeding purposes. It may be kept by a dairy farm as a herd bull, to provide natural breeding for the herd of cows. A bull may service up to 50 or 60 cows during a breeding season. Any more and the sperm count declines, leading to cows "returning to service" (needing to be bred again). A herd bull may only stay for one season, as when most bulls reach over two years old their temperament becomes too unpredictable. Bull calves intended for breeding commonly are bred on specialized dairy breeding farms, not production farms. These farms are the major source of stocks for artificial insemination.
Title: Bulling (cattle)
Content:  Bulling is a behaviour seen in cattle when one mounts another, usually when one or the other is a female in oestrus (on heat); "bulling" is commonly used as a term for a female in oestrus. Female cattle in oestrus may mount any adult cattle, especially a bull (fertile male) if one is present, but they will also mount castrated males or other females. A bulling female will often also be mounted by other cattle, both male and female (only fertile males are usually capable of mating). A dominant bull will defend the bulling female from being mounted by other cattle. Bulling is used by farmers to recognise oestrus, which is important to determine the fertile period when cows may be artificially inseminated. Care is needed to identify whether the animal in oestrus is the one mounting or being mounted, and of course sometimes both animals may be in oestrus. Mounting behaviour is also sometimes seen between adult cattle in the absence of a female in oestrus.
Title: Bull
Content:  bull handling are a significant cause of injury and death for dairy farmers in some parts of the United States. The need to move a bull in and out of its pen to cover cows exposes the handler to serious jeopardy of life and limb. Being trampled, jammed against a wall, or gored by a bull was one of the most frequent causes of death in the dairy industry before 1940. With regard to such risks, one popular farming magazine has suggested, "Handle the bull with a staff and take no chances. The gentle bull, not the vicious one, most often kills or maims his keeper".
Title: Bull
Content:  In many areas, placing rings in bulls' noses to help control them is traditional. The ring is usually made of copper, and is inserted through a small hole cut in the septum of the nose. It is used by attaching a lead rope either directly to it or running through it from a head collar, or for more difficult bulls, a bull pole (or bull staff) may be used. This is a rigid pole about 1 m long with a clip at one end; this attaches to the ring and allows the bull both to be led and to be held away from his handler. An aggressive 
Title: Bull
Content:  Aside from their reproductive duties, bulls are also used in certain sports, including bullfighting and bull riding. They are also incorporated into festivals and folk events such as the Running of the Bulls and were seen in ancient sports such as bull-leaping. Though less common than castrated males, bulls are used as draught oxen in some areas. The once-popular sport of bull-baiting, in which a bull is attacked by specially bred and trained dogs (which came to be known as bulldogs), was banned in England by the Cruelty to Animals Act 1835. As with other animals, some bulls have been regarded as pets. The singer Charo, for instance, has owned a pet bull named Manolo.
Title: Bull
Content:   Bulls are much more muscular than cows, with thicker bones, larger feet, a very muscular neck, and a large, bony head with protective ridges over the eyes. These features assist bulls in fighting for domination over a herd, giving the winner superior access to cows for reproduction. The hair is generally shorter on the body, but the neck and head often have a "mane" of curlier, wooly hair. Bulls are usually about the same height as cows or a little taller, but because of the additional muscle and bone mass, they often weigh far more. Most of the time, a bull has a hump on his shoulders. In horned cattle, the horns of bulls tend to be thicker and somewhat shorter 
Title: Frozen bovine semen
Content:  In a commercially or Custom Stud a bull is generally brought to a collection area where there are gates or other protection areas set up. In most cases of Dairy Bulls the bull has a halter or rope inserted into his nose ring. This is so he can be led and his handler can be a safe distance away, yet have some control over the animal. In the collection area there usually is a stall or stanchion where a mount animal is tied in. A mount animal can be a steer, a cow, or even another bull. Some bulls can be 

Question: what are bulls used for on a farm?
Answer: as work oxen.
slaughtered for meat.
herd maintenance.
breeding.
work oxen for haulage.