When to use antibiotics

Antibiotics can be very effective for certain treatments but are not always the answer. Find out when it is appropriate to administer antibiotics.

Back to: Responsible use of antibiotics in livestock

Antibiotics are categorised into different groups according to their chemical structure and the way in which they kill or halt the growth of bacteria.

Antibiotics vary in the way they are distributed within the body, how long they remain active after dosing, how long they persist in the animal and in the range of bacteria against which they are effective. They are not effective against viruses, although they can be used to control secondary bacterial infections if prescribed by the vet.

Antibiotic use in animals can be divided into three categories:

  1. Curative or therapeutic – treatment of a sick animal or group of animals after the diagnosis of disease or infection has been made.
  2. Control or metaphylactic – treatment of a group of animals after the diagnosis of disease has been made in part of the group. The aim is to treat clinically sick animals and control the spread of disease to others in close contact that may already be subclinically infected.
  3. Preventative or prophylactic – treatment of an animal or group of animals before clinical signs of disease. The aim is to prevent the occurrence of disease or infection.

Antibiotics should not compensate for poor hygiene or inadequate husbandry conditions. For example, the routine use of antibiotics to control watery mouth in newborn lambs is not necessary when:

  • Ewes are adequately fed in late pregnancy
  • Lambs are born into a clean and dry environment
  • Lambs get enough colostrum quickly enough

Some classes of antibiotic, such as colistin, fluoroquinolones and third- and fourth-generation cephalosporins, have been classified as critically important antibiotics for use in humans. Vets are advised only to use these antibiotics as a last resort, when other antibiotics have been, or are expected to be, ineffective.

Whenever possible, and especially in cases where a number of animals are affected, samples should be taken from sick animals and submitted to a laboratory for bacterial culture. The bacteria causing disease can be tested against different antibiotics to identify which ones are likely to be the most effective. This is called antibiotic sensitivity testing.

If an animal is very sick, it may have to be treated before the results are known, but treatment of any further cases can be based on the result of the sensitivity testing. It is important that this testing is done to select the best possible treatment for sick animals and also to monitor antibiotic resistance patterns.

Red Tractor standards specify that your vet must review medicine records and antibiotic use data annually, including the use of HP-CIAs and any prophylactic treatments. Your vet will make recommendations to reduce antibiotic usage, where appropriate, without negatively affecting welfare.

Useful links

Guidance for veterinary surgeons and farmers on responsible use of antibiotics in sheep

Find out more on the farm antibiotics website

See recommendations for measuring and comparing the use of antibiotics on beef farms

See our leaflet on antibiotic resistance: using antibiotics responsibly

Visit AHDB's medicine hub

Using medicines responsibly

If you would like to order a hard copy of Using medicines responsibly, please contact publications@ahdb.org.uk or call 0247 799 0069.