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expert reaction to the continuing horsemeat story and bute (phenylbutazone)

Defra announced the latest results in testing slaughtered horses for bute (phenylbutazone). The presence of bute was confirmed in 8 samples out of 206 tests.


Joint statement from the British Veterinary Association (BVA) and British Equine Veterinary Association (BEVA):

“The presence of phenylbutazone (or bute) in horses intended for the food chain will be of concern to consumers who rightly expect the UK food chain to be robust. We are grateful to the Chief Medical Officer for clarifying the very low level of risk that this presents to human health and we will work with the FSA and Defra in any way we can to assist their investigations into these incidents.

“The ability to treat horses with bute is very important for equine welfare. Bute provides affordable, long-term pain relief for horses and is unique in this respect.

“The UK Horse Passport Regulations are designed to facilitate the ongoing medical treatment of horses not intended for the human food chain, whilst ensuring that these animals do not enter the food chain.

 “We fully support the concept of the Horse Passport Regulations but have argued for some time that there are problems with the system in terms of the number of Passport Issuing Authorities and the vulnerability of the system to fraud. We are very keen to continue our dialogue with Defra and others to find ways to make the system more robust.

“Our members are aware of the strict rules regarding the regulation of medicines (including bute) and the use of horse passports, and in recent years we have provided clear guidance on the regulations to help both vets and their clients. These incidents will hopefully reinforce these messages amongst horse owners and all of us involved in equine healthcare.” 


Professor Peter Lees, Emeritus Professor of Veterinary Pharmacology, Royal Veterinary College, said:

“1. Bute is an excellent pain killer in horses that makes a significant contribution to improved welfare, and has done so for some 60 years.

“2. The main toxicity concern in humans is that some people developed (very rarely – 1 in 30,000 to 1 in 50,000 persons) an anaemia which was life threatening, when the drug was used clinically in humans. This occurred when the drug was used therapeutically in humans at a dose rate of some 2 to 6 mg/kg, similar to the current dose for the horse of 4.4 mg/kg.

“3. The evidence on carcinogenicity in animal studies was equivocal even with high doses (50 to 300mg/kg administered daily for a virtual lifetime-2 years) – if you feed rats enough of many substances they may develop a few more tumours over two years. Carcinogenicity in humans is in the category “not classifiable”.

“4. Calculated human exposure to phenylbutazone and its metabolite oxyphenbutazone from consumption of horse meat, assuming a series of worst case scenarios, is no greater than 1/4,000th of the dose originally given in humans therapeutically. When phenylbutazone was used therapeutically in humans, there were inevitably reported side-effects (as for all drugs) BUT most people given bute for a prolonged period had no serious side effects before it was withdrawn from the human market.”


Professor Tim Morris, veterinary surgeon and Vice Chair of the British Horse Industry Confederation, said:

“Phenylbutazone (often referred to as ‘Bute’) is an anti-inflammatory medicine commonly used in horses, as is a type of medicine similar to aspirin or ibuprofen. It has a good safety record in horses but, as is sometimes found, a different safety profile in people. Some people occasionally suffer a severe adverse reaction to Phenylbutazone, leading to anaemia, hence it is no longer used in people as safer alternatives are available.

“In European law, the horse is regarded as a food producing animal, so as with farm animals there are prohibitions on animals entering the food chain, and horses treated with Bute cannot be humanely slaughtered and then the meat passed into the food chain. To ensure this happens, each horse has its own passport, and for those horses that have had Bute, a section in the passport is amended so the horse cannot enter the food chain.

“If Bute is being found in horsemeat it will be because either the original passport has not been amended after Bute was prescribed by the vet, or because the passport has been altered or substituted, or because controls at the abattoir have failed; all these circumstances are unacceptable as they pose a potential risk to human safety.

“However it is important to note that the levels of Bute in horsemeat, even if it is found, will be very low, and greatly below the doses following medical treatment in people that have been associated with occasional rare adverse reactions; therefore whilst this is unacceptable the actual risk to consumers is very small.”

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