In Ireland, the European Communities (Control of Animal Remedies and their Residues) Regulations 2009 implement the provisions of Council Directives 96/22/EC and 96/23/EC. They prohibit the import, manufacture, sale, supply, administration, or possession of substances having oestrogenic, androgenic, gestagenic, or thyrostatic action and beta-agonists. Limited exceptions are outlined in 96/22/EC for animal remedies that may contain these substances.
The National Residue Control Plan (NRCP), drawn up in accordance with Council Directive 96/23/EC on measures to monitor certain substances and residues in live animals and animal products, is approved by the European Commission and implemented by the Food Safety Authority of Ireland. The scope of testing under the NRCP, for which the Irish Equine Centre is an official laboratory for part of these analyses, is very comprehensive, covering all 11 animal/food areas and 18 distinct residue groups that fall into four broad categories:
- Banned substances, such as growth promoting hormones;
- Approved veterinary medicines;
- Approved animal feed additives; and
- Environmental contaminants.
The extensive testing carried out under this Plan and the low incidence (less than 0.2 percent) of non-compliant samples over the last few years indicate that the controls in place are ensuring that the administration of banned growth promoting hormones and banned substances to food-producing animals in Ireland remains low or those illegally using these substances have evaded detection.
Growth promoters, which are tested for under the NRCP, are hormonal and antibiotic substances that may be used in food producing animals for growth promotion in livestock animals, thus increasing the production of muscle meat and the reduction of fat. The type of growth promoter used is dependent on the animal species and mode of rearing—with steroid growth promoters used for beef cattle and antibiotic growth promoters, which are usually added to feedstuffs, such as the coccidiostats used in the poultry industry and chlorotetracycline used in the porcine industry.
It is not clear what the potential human health impacts of growth promoters are, particularly when it is possible that exposure may be extended over long periods of time. Of the hormonal growth promoters (anabolic steroids) the use of three natural steroids (17β-estradiol, progesterone, and testosterone) and three synthetic hormones (zeranol, trenbolone acetate, and progestin melengestrol acetate) have been banned in the EU since 1988. For all of these six hormones, endocrine, developmental, immunological, neurobiological, immunotoxic, genotoxic, and carcinogenic effects could be possible. Of the various susceptible risk groups, prepubertal children is the group that was reported to be of greatest concern by a report on the Opinion of the Scientific Committee on Veterinary Measures Relating to Public Health (SCVPH)—April 10, 2002 (on review of previous SCVPH opinions of April 30, 1999 and May 3, 2000 on the potential risks to human health from hormone residues in bovine meat and meat products). Therefore, from a consumer health perspective, it is essential that testing is carried out for these substances.
Of the antibiotic growth promoters, prophylactic use is common practice in animal feed and can be vital for animal health, particularly with intensified animal rearing. Suppression of disease causing organisms by prophylactic use of antibiotics may reduce the incidence of clinical and subclinical disease, resulting in better animal health and growth. The same classes of antibiotics used to treat humans are given to animals. A report by the U.S. FDA in 2013 revealed that the meat industry accounts for nearly four fifths of all antibiotics used. The issue of antibiotic resistance is of paramount concern. If antibiotics are administered at a therapeutic level (in the absence of prophylactic use), the consumer may be exposed to the antibiotic particularly if it’s not used judiciously with observation of withdrawal times so that maximum residue limits (MRLs) are not breached. This in turn could potentiate the issue of antibiotic resistance, which will affect all species.
Due to the economic benefits to be gained from the use of illegal growth promoters, they will continue to be used in animal production. As analytical methods of detection become more sensitive, methods of evasion have become more sophisticated. The ban on the use of steroid implants (which were easily detected upon ante-mortem inspection) resulted in the production and distribution of liquid-based steroid formulations. The use of low-dose multi-compound cocktails, which are below detectable levels but have a synergistic effect when used together, and natural hormone administrations such as 17β-estradiol, make detection and confirmation of these substances difficult. This in turn presents an enormous challenge to regulatory authorities tasked with enforcing their ban.