Bute residue showing up in UK horses even with vaunted "passport" system

UK vets have 'repeatedly raised concerns' over bute in food

An independent veterinary committee had "repeatedly expressed concern" about a drug found in UK horsemeat destined for export, the BBC has learned.

The discovery of horsemeat in UK foodstuffs is raising big concerns that UK testing regimes are not sufficient.

There are worries that if unregulated horsemeat is substituted for beef it could expose people to a drug called phenylbutazone - often called "bute".

Once used as an anti-inflammatory, its toxicity to some people led to a ban.

The drug in rare cases caused a serious blood disorder known as aplastic anaemia.

But it is still used widely to treat horses. Once treated these animals are not supposed to enter the food chain.  ..... 

Last July the UK's Veterinary Residues Committee, which carries out that testing, issued a report. In it, they showed that among 60 samples of horsemeat destined for export in 2010, there were five positive results for bute.

(My Note: 5 positive results out of 60 sampled is a 9% rate, not 5% as implied in the article)