How are antibiotics administered to farm animals, eg in feed?
When treating farm animals against bacterial disease, antibiotics are most commonly administered in the same way as for humans – orally or by injection. Oral administration can include by bolus, tablet or paste, or as a powder or solution in feed or drinking water. The method of administration is usually a matter for the prescribing vet to determine, and will often depend on the species being treated, the numbers needing treatment, and other factors such as the handling facilities available and the risk of stress for the animal. Stress is a major consideration as the animal being treated should be either clinically infected or at high risk of being infected at the time of treatment, and exposure to stress can further impair its immune system.
The situations where antibiotics are administered in feed are usually where there are large numbers that require treatment and when it’s the most practical option available. In this situation the medicine will usually be added to the feed upon receipt of the veterinary surgeon’s prescription at the feed mill.
Some farms have a facility to add a medicine to drinking water. This can result in increased accuracy as while intake of feed can vary between animals, they tend to drink more uniform quantities. However, if animals are outside, they will usually drink from rainwater sources as well as piped sources, risking any treatments being taken in at levels that are below the prescribed dose rate. In these situations, administration via feed can be the only practical option, for example with a herd of outdoor sows.
The most accurate method of application is to individual animals via injection or oral tablet or paste, after weighing to ensure an accurate dose rate is applied. In reality, this happens more often with cattle and sheep as the numbers per farm are generally fewer and they are easier to handle or bring inside for treatment. In pigs and particularly poultry, it is often impractical and counterproductive to treat individual animals although this can sometimes be an option.
It is important to note that routine preventative use of antibiotics is not supported by RUMA or UK veterinary associations. Use of antibiotics as a growth promoter, commonly applied via feed, has also not been permitted in Europe since 2006.
In countries outside Europe where growth promotion in animals is permitted, antibiotics can be given to the animal on an ongoing basis at sub-therapeutic dose levels, which is different from situations where a veterinary surgeon prescribes a defined course of antibiotics at a clinically approved dose level to treat or prevent a specific disease challenge. Hence treatment of animals for disease via in-feed antibiotics should not be confused with use of antibiotics for growth promotion through feed.