Detection and Control of Unregistered Growth Promoters in Veal
John Patterson, Adrian Fesser, Stephen Lee, Ron Gedir, Geoff Gerhardt and Jim MacNeil
The Canadian Food Inspection Agency is responsible for meat inspection at federally registered slaughter establishments. This includes monitoring for drug residues and enforcing Maximum Residue Limits (MRL) set by Health Canada. Random testing is conducted each year for a wide variety of veterinary drugs and in most cases the industry is close to 100% compliance with regulations governing drug residues. In recent years the main exception to this has been residues of growth promoters in veal at slaughter, especially in milk-fed or "white" veal. Prior to 1996 there were rumours of widespread abuse of clenbuterol in veal production, but testing of liver and urine by LC-UV revealed very few detectable residues. Clenbuterol is the most popular of a large class of drugs known as the -agonists, which are used therapeutically as broncho-dilators, but have potent growth promoting effects at higher doses. Clenbuterol is known to bind to melanin and after switching to retina (a highly pigmented tissue) as the target tissue and introducing LC-MS-MS to the testing procedure, the 1996 survey found clenbuterol residues in 13% of veal samples. There are reports from Europe of acute toxic effects in people who consumed liver which contained high levels of clenbuterol. With this information and the evidence of clenbuterol abuse by veal producers, the Bureau of Veterinary Drugs (Health Canada) banned the use of clenbuterol in food producing animals. Since that time veal producers with a record of clenbuterol use have had subsequent shipments held and tested. The meat from these shipments is released only if no detectable residues are found. This has essentially eliminated the use of clenbuterol and residues in retina are seldom found. As clenbuterol abuse was being suppressed, a significant proportion of veal producers adopted trenbolone acetate as the growth promoter of choice. Trenbolone is a synthetic analogue of testosterone and is approved for use in cattle with an MRL of 2 ng/g in muscle and 10 ng/g in liver. It has not however been approved for use in veal calves. Detectable trenbolone residues are seldom seen in tissues of cattle, but accumulate in the liver of milk-fed veal. Random surveys in 1997 showed that 28.7% of veal liver contained residues of trenbolone at >10 ng/g. A hold and test policy was implemented for trenbolone residues and compliance is now close to 100%.
We continue to monitor for growth promoters in all species and improve our analytical capability. A multi-residue LC-MS-MS method for -agonists is in the final stage of development. We will also be investigating the application of capillary electrophoresis with electrochemical detection to drug residue problems.
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