Defra is the Government department that deals with livestock, along with the Animal Health Agency. Good luck translating what they say into English!
A cattle example: I am in a 4 year TB zone. Each calf at birth is tagged with two tags carrying a unique individual number, comprising my herd number plus an animal number (eg UK123456 100056). This info is sent to government. At minimum you need calf identity, dam identity, breed, date of birth, place of birth. Every veterinary treatment must be recorded for this individual. All medicines must be safely stored and accounted for. All withdrawal periods must be followed. I can move this animal to another holding, and I must tell the government which animal had moved, from where to where, what date, what vehicle. Once there, nothing can leave that holding for 6 days. I can get special exceptions to go to a show.
I can't transport the animal in certain conditions (eg very pregnant). The trailer must be washed out thoroughly after each use. At sale, slaughter, or death I have to notify the government. I cannot allow manure or slurry to foul water courses, and I cannot allow damage to river banks from drinking/trampling.
I have probably forgotten a whole load. I use a software package that collects more data than legally need, but that is useful/good practice to record.
I have it easy! If you are TB tested more frequently, then you have to repeat the TB test before your animal moves of your holding. This in itself is a 4 day procedure.
TB testing is compulsory at least every four years, for your whole herd. Any positive results mean that animal is destroyed and you go into a routine of repeat tests. You can lose your entire herd.