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Antimicrobial Resistance


Antimicrobial resistance

There is increasing concern worldwide about the development of antimicrobial resistance and the increasing number of deaths as a result of bacterial infections that are not curable with currently available antibiotics, O’Neill Report (2016).  Farmed livestock are major consumers of antibiotics and there is concern that antibiotic resistance would develop in livestock and then be transferred to people.  While a link between use of antibiotics in livestock and antimicrobial resistance in people may not be easy to confirm, nevertheless a report across 7 European countries found that there was a high and direct correlation between antibiotic use, (in livestock), in each of these countries and the amount of antimicrobial resistance found in livestock in each country.

A number of countries have sought to quantify livestock antibiotic use, both nationally and at farm level for specific enterprises.  These studies have highlighted a vast range in the amount of antibiotics administered on farm and also in the range of metrics used to measure antibiotic use. 

The metrics used to quantify usage are many and varied and there does not seem to be a standard system that is used across countries to allow a meaningful comparison.  The UK has adopted the metric of ‘milligrams antibiotic per population correction unit’, (PCU).  PCU allows across species comparison, taking into account the mass of livestock.  It has some inherent weaknesses, as do all the different metrics that are used to measure antibiotic consumption, whether at farm level, national level or at international level. 


The Responsible Use of Medicines in Agriculture Alliance, (RUMA), is an independent not for profit organisation that represents all stages of the food chain from ‘farm to fork’.  They monitor sales of antimicrobials across species in the UK and have set targets for each species type, to be achieved by 2020.  The target for dairy cows by 2020 is 21 mg/PCU, with less than 0.538 mg/PCU coming from highest priority critically important antibiotics, (HP-CIA’s).  These are antibiotics that are largely reserved for use in humans.  This target of 0.538mg/PCU for HP-CIA’s is now largely redundant as far as NI dairy producers are concerned.  This is because new Red Tractor standards for antimicrobial use have been introduced and the vast majority, if not all dairy producers in NI have to adhere to these standards due to the milk processers accreditation under this scheme.  With Red Tractor regulations, HP-CIA’s can only be used following bacterial sensitivity testing, which must show that no other lesser important antibiotic will be effective.  In effect, this is highly unlikely to be true, so ruling out the need for HP-CIA’s in dairy cattle.

Analysis of medicine records

Dairy farmers are required to record all purchases of medicines and all administrations of same.  These records are available to Farm Quality Insurance and Red Tractor Inspectors.  Going forward, there will be much more scrutiny of these records.  Inadequate record keeping is a major reason for failing an inspection.  Computer software packages and mobile phone apps can greatly enhance the record keeping process, together with the potential benefits that can be gained from analysing the data recorded.  A number of veterinary practices in N.I. have software which allows collation of antibiotics sold to individual farms and this can be used for quality assurance inspection purposes.  Some farms have the equivalent software on farm, (or other equivalent software packages), to allow recording of drugs received from the veterinary practitioner and the details of administration to farm animals.  This is very useful for Red Tractor Inspections, when medicine use over the past year can be easily extracted and signed off by the farm veterinary practitioner. 

It is likely that antibiotic use in farm animals will come under increasing scrutiny, as will the impetus to reduce use in farm animals.  Good records of purchases and usage is a pre-requisite to this process. 

An essential component in bringing about change on farms is the ability to measure the difference you are making.  William Thomson, (Lord Kelvin), the mathematical physicist and engineer, famously said, ‘When you can measure what you are speaking about and express it in numbers, you know something about it; but when you cannot measure it . . . your knowledge is of a meagre and unsatisfactory kind.  This can undoubtedly be applied to the area of antimicrobial use and its potential reduction on farms, particularly as medicine purchases and administration of same are often poorly recorded and seldom used in any meaningful way.

The most influential source of information on antimicrobial use is the farmers’ own veterinarian and hence, the vet-farmer relationship plays a very important part in the reduction of antibiotic use on farm.  Vets are prescribers of antibiotics and are responsible for how they are used on farm, whether administered by them or not.  They have a very important role to play in their interaction with the farmer and the influences they bring.

Antimicrobial benchmarking tool

A tool has been development by Nottingham University, which gives the total antibiotic use per PCU and also on a doses per cow and courses per cow basis.  The tool can be downloaded using this link.

Reducing antimicrobial use on farm

Animal health plan

Each farm should have an animal health plan, written in conjunction with the farm veterinary practitioner, which is reviewed at least annually. (Part of Red Tractor Standards).  This should be a working document, referred to regularly and contain information on aspects of all animal health, such as bio-security, vaccinations, parasite control, lameness management, etc.  By reviewing this document at least annually and measuring what antimicrobials are being used and by what type of livestock, it is possible to see where the pinch points are and subsequently, to develop a plan in conjunction with the farm veterinary practitioner, to reduce the need for antibiotic use going forward.


The biggest use of antibiotics administered on dairy farms are injections, as they contain much larger volumes of antibiotics, compared to lactating and dry cow tubes.  Hence, it is important to review why injections are given: mastitis, lameness, post calving malaise, etc, and work with your vet to find the pinch points and consequently chart a way to reduce the need for injections to be given in the first instance.   

Selective Dry Cow Therapy

This is a relatively simple, but effective method to reduce the need for dry cow tubes.  However, milk recording is an essential tool to allow decisions to be made as to what cows should receive dry cow tubes, (usually combined with internal teat sealants), and what cows should receive teat sealants only.

Good hygiene at drying off is absolutely crucial to good outcomes, but if the correct procedures are followed, there should be no dead cows within two days following drying off!  For more information, please follow this link: selective dry cow therapy.