| 4.5°C Dublin

Watch out for long withdrawal periods

I had a query the other day about withholding times for certain medicines before slaughter. It opened up a minefield of a conversation where I explained the ramifications of the use of some products in forward beef cattle.

In most cases, it's easy enough. The bullock has an infection. He needs an antibiotic and therefore must not be slaughtered for 28 days after the last day of the injections.

The withdrawal period is 28 days and this is worked out between the manufacturer and the licensing authority, the Irish Medicines Board. It's written on the bottle and the veterinary practitioner states it and records it on the prescription docket at the time of dispense. That sick animal is not likely to be presented for sale or slaughter in the near future as he'll need time to return to full health and potential.

Where the issue of withholding becomes more difficult is where anti-parasitic treatments are used. Here, the withholding time or withdrawal period before slaughter can be slightly longer. So, a beef farmer notices his cattle are in need of worm or fluke treatment late in the autumn. With changing trends in parasites, we see a greater need for parasite treatment in older cattle -- more than was the case years ago. As cattle are coming close to their slaughter date, some are being held back by worms or fluke.

Depending on the dose used, we can see withdrawal periods of 60 days or more in certain products. This means that cattle dosed in late autumn, say early October, cannot be slaughtered until early December. Again, all is OK as long as the cattle are not sold to a factory supplier in mid-November. This factory supplier may unwittingly sell on to the factory before the end of the withdrawal period. And so, meat residue levels could be exceeded. Nowadays, a certificate of compliance on medicine residues must accompany all cattle arriving at the factory and that certificate is to prevent animals being slaughtered before the full withdrawal periods are expired.

The farmer or supplier must sign the form, but may do so without all the correct knowledge or details.

The waters get further muddied in the case of red-water treatments. In this case, a forward store falls foul of the blood-sucking tick and is presented to the vet as a life-threatening case of red-water. The correct product is used to kill the Babesia blood parasite, but the withholding time is 210 days (seven months). The forward store makes a marvellous recovery and may be good enough to be sold on in a matter of weeks.

He enters a fattening unit and, lo and behold, he's ready for slaughter well before the seven months are up. To help the story, let's imagine the bullock was sold several times before the final fattening. Now, whose signature goes on the certificate at entry to the factory? Whose head is on the block if the withholding time of seven months is not observed?

Needless to say our conversation bounced around many different angles of this topic. We also spoke of Alberto Contador, the Tour de France-winning cyclist, who claims the clenbuterol levels in his blood came from meat produced in Spain. With testing abilities nowadays, they can detect very, very low amounts of any residue -- right down to an individual molecule of a drug. The testing techniques are so good and the levels being found are so small that some worrying scenarios are beginning to arise.

In the case of Contador, no clenbuterol should ever be used in any food-producing animals. Zero tolerance exists. But with some medicines, we may have procaine -- a local anaesthetic -- being used as a mixing agent in our penicillin, for instance. The athlete who competes under zero tolerance of local anaesthetics eats meat that did observe correct withdrawals after penicillin use. Can the local anaesthetic part contaminate an athlete's blood if the testing techniques are so ultra-sensitive? The mind boggles.

Suffice to say, that for us vets and farmers, we must ensure all withdrawal periods are fully observed, and if cattle are being sold on before withdrawal time is complete, then the correct information must also be passed up the chain.

I never want to hear Irish meat being blamed as a source of a restricted substance.

Peadar O Scanaill is a veterinary practitioner in Ashbourne, Co Meath, and is a member of Veterinary Ireland's Animal Health Committee. Email:

Irish Independent