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Antibiotic resistance and food

The possible association between antibiotics used routinely to protect the health of animals raised for food and the growing resistance to antibiotics by some micro-organisms, is causing concern within New Zealand and internationally.

Antibiotic resistance and the issues for food

Certain strains of bacteria have now evolved with the ability to survive exposure to some antibiotics. Human Tb is on the rise worldwide again and other new strains of bacteria like MRSA (methicillin resistant Staphylococcus aureus) have been found in some hospitals.

Limited overseas evidence indicates that in some specific instances, the use of antibiotics in animals may contribute to the level of antibiotic resistance in humans. Since 1972, the New Zealand Ministry of Health has monitored antibiotic resistance for important human bacterial pathogens (disease causing micro-organisms). There is no evidence to date from this monitoring that the use of in-feed antibiotics has lead to resistance.

Although antibiotic use in animals may not be a significant contributor to antibiotic resistance, evidence of such trends is continually monitored and regulatory control will be adjusted if necessary. At the same time, the prudent use of antibiotics in animals must be encouraged for the health and welfare of the animals concerned.

What antibiotics are and why they are used

Antibiotics are chemical substances used to fight infections in humans and animals. They are capable of destroying or preventing the growth of bacteria.

The first antibiotic compounds used in modern medicine were Penicillin - discovered by Sir Alexander Fleming in the 1920s. Penicillin revolutionised the treatment of, what were then, life-threatening bacterial infections eg, human tuberculosis (Tb), pneumonia and wound infections.

How antibiotics are used in animals

Like humans, animals need antibiotics to fight off bacterial infections. The use of antibiotics in cattle and sheep is relatively low due to the pastoral farming systems in New Zealand. Use tends to be higher in the intensive rearing industries, mainly the pig and poultry industries.

Antibiotic use in animals in New Zealand falls into two areas:

1. For medicinal or therapeutic use - when the individual animal or groups of animals are ill and show symptoms of disease. Most antibiotics are used for this purpose.

2. For preventative or prophylactic use - as a safeguard when there is a high probability that animals will catch diseases, including when disease is already appearing in a group of animals. For example, a common disease in chickens is necrotic enteritis, a gut disease. When kept together in sheds or barns this disease spreads quickly, so antibiotics may be given to chickens in their feed to prevent it spreading.

Internationally, antibiotics may also be used for growth promotion. In intensive rearing situations, healthy food animals may be fed very low doses for long periods to increase the rate and efficiency of the growth of the animal. In New Zealand however, using antibiotics for growth promotion is only approved for those antibiotic products that don’t contribute to the development of antibiotic resistance.

Control of antibiotics for animals raised for food

When animals are treated with antibiotics, a certain period of time must elapse (the withholding period), before they can be sent for slaughter. This ensures that the medicine has done its job and passed out of the animal's system. As a further safeguard, any residual antibiotics must meet the Maximum Residue Limit (MRL) food standard. Compliance with this ensures there is no food safety concern over any residual trace present in the food produced. Coincidently, the MRL also ensures that any antibiotic that might still be present will not be enough to contribute to the development of resistance.

All antibiotics registered for mass medication of animals in New Zealand have been assessed against thorough review criteria. They have been reviewed for veterinary use and human health significance as agreed with the Ministry of Health. Where the potential for resistance problems has been identified in antibiotics of human health significance, action has been taken. This action includes removing growth promotion as an approved use for all antibiotic products except those known not to contribute to the development of resistance. In addition, the requirement for a veterinary prescription before sale or use for those antibiotics identified with the potential for resistance problems.

New Zealand has taken a conservative and precautionary position on this issue. In a country dependent upon our reputation as a producer of safe food, protecting our animal welfare and human health are priorities. We are confident that the actions taken in regard to antibiotic resistance have us well positioned to continue to safeguard this reputation and public health.

Why antibiotic use in animals has not stopped

Antibiotics are essential for the health and welfare of animals. The livestock industry is investigating alternatives to antibiotics, but in many cases antibiotics must still be used to ensure the health and welfare of animals.

Additional Information

Antibiotic resistance and in-feed use of antibiotics in New Zealand - technical information

Detailed frequently asked questions about Antibiotic resistance and food

Antibiotic resistance - am I at risk? [Ministry of Health]

Page last updated: October 2007