What Actually Are Veterinary Drugs?“Maximum Residue Limits of Veterinary Drugs in Food”


Veterinary drug residues are one of the important factors affecting the safety of animal-derived food. With improvements in living standards and growing demand for animal-derived food, veterinary drugs are commonly used in animal husbandry to prevent and treat animal diseases. However, improper use of veterinary drugs may cause various problems, such as drug resistance. Owing to this, international standards for limits of veterinary drug residues in animal-derived food have been established to ensure the quality and safety of agricultural products. It regulates the rational and scientific use of veterinary drugs in animal husbandry to prevent their residues from exceeding the enacted limits and causing hazards to human health. Back in May 2013, Macao government has promulgated the ‘Maximum Residue Limits of Veterinary Drugs in Food’ to control the maximum residue limits1 of any drugs in the edible parts of food animals, including cattle, pigs, chickens, sheep, goats, horses, poultry, fish, shrimps, etc. A total of 18 veterinary drugs classified into 10 types of drugs are subject to be regulated.


Why are veterinary drugs used?

For raising livestock and poultry in an intensive capacity, the feeding management and excreta treatment can be centralised to increase efficiency. However, high-density feeding inevitably accelerates the spread of epidemic diseases in livestock and affects their growth. Animals, like humans, suffer from sickness and require proper treatment. Veterinary drugs are used for therapeutic, prophylactic and diagnostic purposes in food animals.


What are the veterinary drug residues in food?

Veterinary drug residues refer to any drugs or relevant substances which remain in the edible parts of food animals after treatment. Although veterinary drugs break down into other substances over time, it may leave residues in the animal body. These residues can be the veterinary drug itself or the products of decomposition. The amount and property of the residues as well as the time required for decomposition vary across different veterinary drugs. Consumption of food containing excessive veterinary drug residues over extended periods may result in acute or chronic poisoning. In mild cases, the symptoms are allergic reactions and headache. Chronic poisoning can cause damage to the liver, kidneys and nervous system.


Should veterinary drugs be completely banned from the use in food animals?

The veterinary drugs in the regulation include antibiotics, antimicrobials, anthelmintic and β2-adrenergic agonists (commonly known as leanness-enhancing agents), which are used to stabilise and improve the quantity and quality of food animals, promote their health and growth, as well as increase production efficiency. Proper and correct use of veterinary drugs in appropriate dosage has positive effects.


Regulation of the maximum residue limits of veterinary drugs in food in Macao

To strengthen the monitoring and control of veterinary drug residues and ensure the safety and health of animal-derived food, the Administrative Regulation No. 13/2013 ‘Maximum Residue Limits of Veterinary Drugs in Food’ clearly defines the highest concentration of different veterinary drugs permitted in different edible parts of animals. All fresh and live food products are subject to mandatory inspection and quarantine before imported to Macao. Only the qualified suppliers are permitted to import the live pigs and cattle from their livestock farms to Macau. The inspection procedures include entry inspection, ante-mortem examination, post-mortem examination and sampling tests. The veterinarians conduct organoleptic examination of the carcass and offal from the slaughtered animals. Any carcass or offal found to have pathologic changes will be destroyed instantly. Moreover, the urine, carcass and offal of animals are sampled for veterinary drug residue tests to ensure that the food animals comply with legal standards and are safe for consumption.


How should the public reduce the risk of intake of veterinary drug residues?

Though we cannot determine the presence of veterinary drug residues in food by its appearance, consumers should not be overly worried. They should follow the dietary advices below to prevent and reduce intake of veterinary drug residues in food.

  • Livestock farms in China dedicated as food suppliers to Macao are under the stringent regulation and inspection by China government. The farms are required to obey the withdrawal period, refrain from the use of antimicrobials/antibiotics intended for human use and control the administered dosages of drugs so as to reduce the risk of veterinary drug residues in food. Moreover, consumers should buy food products from reputable shops in Macao, and the food industry must not sell food products from unknown sources.
  • Eat a variety of food and maintain a balanced diet. Avoid consumption of animal offal or a single food type over extended periods of time. It helps to reduce health hazards from excessive intake of a single contaminant.


‘Maximum residue limits’ refer to the highest concentration of residues of veterinary drugs legally permitted in food or on the surface of food, expressed in mg/kg, μg/kg, mg/L or μg/L.