Use of any antimicrobial drug for any treatment can lead to the development of resistance. As a population is introduced to a drug’s chemistry, solutions are reached to nullify the drug’s effect.

Antimicrobial Resistance - How Is Veterinary Medicine Contributing to Resistance?

However, there is global consensus now among medics and veterinarians that, by not using antimicrobial technologies in the optimal way, and in some cases over relying on them, resistance is being accelerated.

Generally, this could mean stopping a course of drugs too early, or prescribing drugs at too low a dose to combat infections.

Antibiotics may be used therapeutically to treat an existing infection, but there is also the routine use of antimicrobials, where drugs are issued to prevent illness or boost health without signs of infection being present.

Routine use of antimicrobials is common in some of the world’s livestock systems, especially in more intensive operations where animals are housed close together.

Veterinarians talk of two types of routine use:

  • Prophylactic – Medicine given to prevent illness rather than fight infection. This could be following or in anticipation of the animal going through a period of stress, such as an operation.
  • Metaphylactic – Administering treatment to the entire herd or flock due to the potential infection risk increasing through proximity to infection or the conditions in which the animals are kept.
Antimicrobial Resistance - How Is Veterinary Medicine Contributing to Resistance?

Trucking cattle to feedlots over 1,000 miles away is not uncommon in the United States and is carried out in all weather conditions.

Examples of routine antimicrobial use extend throughout all livestock sectors and have been practised the world over. For example, it was standard European practice to give a pig antibiotics to promote health after tail docking. It still is widely practiced to give cattle antimicrobials in the US after lengthy periods spent in transit to help them through what is known as ‘shipping fever’.

An easy way to administer antimicrobials this way is through incorporation in feed or water. This method saves time when farming on a large-scale, such as commercial poultry and pig units, the two types of operations that experts most associate with antimicrobial resistance. Dairy farms routinely use antibiotics to tackle mastitis through the dry-cow period.

Such routine uses are also known as non-therapeutic or sub-therapeutic uses, since no signs of infection exist prior to the administration of antibiotics. However, veterinary guidelines, legislative changes and some policy measures have started to reduce this, with action being taken in the European Union and the US.

For example, the European Union started to gradually withdraw antibiotic growth promoters (AGP), an example of non-therapeutic use of antibiotics, between 1995 and 1999 as a ‘precautionary principle’ and then banned AGPs in 2006.

Many countries still allow antimicrobial medicines to be fed sub-therapeutically but the US has now concluded that AGPs are not in the best interest of public health.

Antimicrobial Resistance