In the United States, in the trucking business, a bullrack is a trailer used in the transportation of cattle. These trailers have many vents to allow for air flow, a necessary but malodorous defining feature. Follow a bullrack down the road with your windows down in summer and little doubt remains as to the freight on the trailer, bull squeezin's having a very definitive scent.
The number of bulls transported is a rather small percentage of total head of stock hauled, as bulls are usually neutered to foster faster growth and provide for easier, safer management.
Transporting an animal which weights from a few hundred pounds to almost a ton is difficult enough, but with the addition of testosterone it becomes a very dangerous task indeed. Removal of the testicles is a quick and simple solution which has been used for many years.
Actual bulls, testosterone producing equipment intact, which are hauled are usually breeding stock. This is also a shrinking business as artificial breeding methods are commonly used. Old Bossy can have her calves without ever going on a date. Rodeo bulls are also transported in bullracks from venue to venue.
Bullrack then is a generic term for a trailer used to haul cattle rather than being gender specific.
Other trailers with different characteristics are used to transport different kinds of livestock. An example would be a trailer used to haul swine, which is usually a double deck affair. Pigs need far less headroom, allowing for more than one level for the hapless passengers.
Over 30 years personal experience in trucking.