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Bute Found in Contaminated Horse Meat: Does it Pose a Risk?

Bute Found in Contaminated Horse Meat: Does it Pose a Risk?

As the ‘horse meat scandal’ continues to develop, concern has been growing over the possible danger that bute (phenylbutazone) may impose on human health.

In this article, we’ll be discussing what bute is and why it is used, as well as the risks that it may (or may not) carry.

Also covered below are the recent results from the FSA concerning contaminated horse carcasses destined for human consumption and the importance of horse passports (and why they are current failing).

What is Bute?

Phenylbutazone (bute) is a non-steroidal anti-inflammatory drug (NSAID) commonly used as a pain reliever in horses. Bute reduces inflammation and pain by inhibiting enzymes responsible for the production of prostaglandins (a hormone involved in inflammation/pain).

Bute was once used in humans, but is now no longer approved in the USA. It is still used in the UK, but only for the treatment of ankylosing spondylitis (a type of arthritis that can cause extremely painful and debilitating fusion of the spine) when other treatments aren’t suitable or available.

Benefits of Bute Use in Horses

Bute is an effective pain reliever that is commonly used in horses. Its widespread use is owed to its easy available and low cost. It is primarily used to treat lameness and offers pain relief from a number of ailments including:

  • Infections
  • Muscle sprains or injuries
  • Joint pain
  • Arthritis
  • Tendinitis
  • Laminitis

Bute reduces the inflammation and fever associated with these conditions, reducing pain, however; chronic use of bute, or overdosing can cause ulceration of the gastrointestinal tract.

See here for more information on the use of bute in horses.

Does Bute in Horse Meat Pose a Risk to Human Health?

The UK, EU and USA do not allow the use of bute in horses at any point in their life if they are intended for human consumption. This is due the serious and potentially lethal adverse effects it has been known to cause in humans.

Around 1 in 30,000 patients suffered from a serious and potentially lethal condition known as aplastic anaemia when taking bute. The bone marrow of patients suffering from aplastic anaemia becomes unable to replenish blood cells (red blood cells, white blood cells and platelets).

Many race horses are often destined for slaughter for human consumption and it is these horses that are most likely to be treated with bute. It is the responsibility of the abattoir to check the documentation of horses intended for human consumption and dispose of those where bute administration has been recorded. This information is contained within a horse passport (see below).

It remains unknown how long bute and its metabolites remain in the body. Fortunately, highest concentrations are found in the horse’s blood, kidneys and liver – components that are not included in the ‘dressed meat’ intended for human consumption. The muscle tissue that is consumed, contains the lowest levels of bute.

Whilst it is highly likely that bute contaminated meat is able to make its way in to the human food chain (as demonstrated by recent events), the risk to human health is actually relatively low. See below for more information on the recent carcass test results from the UK Food Standards Agency (FSA).

How Horse Passports ‘Prevent’ Bute from Entering the Human Food Chain

horse passport example

All horse owners must now obtain a passport for each horse they own, if the horse is intended for slaughter for human consumption at the end of its life, the owner should sign the corresponding declaration.

The passport acts as a method of identification for the horse, by allowing the owner to record physical traits and characteristics. The passport also acts as a log of any medications (or notifiable illnesses) the horse has been administered during its lifetime. If bute is recorded in this section, the horse may not be slaughtered for human consumption and will be disposed of at the abattoir.

Whilst in theory this works, a lack of centralised regulation makes it easy to circumvent the restrictions regarding medication and slaughter for human consumption. There are over 80 equine passport delivery bodies (PIOs) and the government run national equine database (NED) has been retired; without the NED it is easy for horse owners to commit passport fraud and apply for additional horse passports.

By applying for an additional passport, a horse owner is able to omit details about bute administration, thus allowing the horse to be slaughtered at the abattoir for human consumption.

Currently around 9,000 horses are slaughtered in the UK each year for human consumption, however, all of this meat is exported.

FSA Testing of Horse Carcasses for Bute

A recent investigation by the FSA involved testing 206 horse carcasses, slaughtered in the UK between 30/01/13 – 7/02/13, for bute residue. They recorded 8 positive results for bute (4%)

The highest amount of residue recorded was 1.9mg per kg of meat – which is actually a relatively small amount. To put this in to perspective, a single serving of 250g of 100% horse meat would contain around 0.5mg of bute. The typical dose given to humans is 100mg, 200x the amount found in a single serving of contaminated meat.

The conclusion is that whilst a risk to public health is present, it is negligible.

Further Reading

Association of phenylbutazone usage with horses bought for slaughter: A public health risk – An American paper from a few years ago that indicates how poorly controlled bute-contaminated horse meat is, and how easily it is able to enter the human food chain.

The European trade in horsemeat mapped – An interactive map documenting the trade of over 60,000 tonnes of horse meat by European countries in 2012.

About James Watts

BSc Bioveterinary Science. Editor of PetSci. When I'm not writing, learning, discussing, or reading about animals, you know it's the weekend!

2 comments

  1. Contaminated horse meat has entered the food chain of racing greyhounds. Their regulators suggest skuldgery i.e. trainers are inappropriately using bute as a pain killer. Does your research identify the level or content per kilo? Reading on the internet seems to suggest higher contamination from different parts of the body. Thanks Chris

    • Hi Chris, you’re correct, levels of bute do differ between regions of the body. It is found in highest concentrations in filtration organs such as the liver and kidneys.

      Fortunately, ‘horse meat’ consists mainly of horse muscle, which is where bute is found in the lowest concentration.

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