Avoid antibiotic residues in milk

Antibiotics are present in cow's milk that is undergoing treatment and these substances can cause various problems.

Among them, we can mention:

Change in the microbiota of milk

The antibiotics present in milk cause the inhibition of lactic acid bacteria, even if only partially.

Even if this milk goes through a pasteurization process, the activity of antibiotics is not less. They are not eliminated by the high temperature and only traces of these substances can inhibit the lactic ferment bacteria.

Isso já é um impacto grande, tendo em vista que podem alterar o processo de fermentação, reduzir o pH, além de comprometer a qualidade dos derivados desse leite, podendo ocasionar a parada total e perda do produto na fabricação de queijos.

In addition, with the imbalance of the normal microbiota in milk, pathogenic bacteria and coliforms have the opportunity to grow in this product.

Microbiological risks 

Generally, much of the human population is exposed to low doses of antibiotic residues in milk. However, in the long term, serious effects may be noticed. 

The presence of antibiotic residues can select for resistant strains of bacteria in humans, as well as kill natural bacteria in the intestinal tract, creating an imbalance in the intestinal flora. 

Bacterial resistance is a subject that is often addressed by the World Health Organization (WHO) in view of its degree of relevance to public health.

This is because this resistance has made drugs that were said to be gold treatments become ineffective in combating pathogenic microorganisms.

Thus, the result is an increase in mortality and morbidity rates in the population, with the most diverse diseases with ineffective treatments. 

Immunopathological risks

Antibiotic residues can also generate hypersensitivity and anaphylactic shock in humans. 

There are people who are very sensitive to antibiotics, who develop several unpleasant reactions after ingesting contaminated milk.

Many antibiotics can be used in cattle, including penicillin. 

In this scenario, 5 to 10% of the world's population are hypersensitive to this drug, so very small amounts in milk are enough to trigger an allergic process.

Toxicological risks

In terms of toxicological risks, the most affected consumers are pregnant women.

This is because the fetus exposed to these antibiotic residues may suffer from the teratogenic effects of these drugs.

In addition, contaminated milk can cause toxicity and changes in fetal bone development.

Environmental risks 

We cannot forget that, in addition to the damage to the dairy industry and final consumers, antibiotic residues can generate environmental risks.

This danger is due to the fact that the waste goes into the aquatic environment during disposal, when the presence of these substances is detected, for example.

Conditions that cause the presence of antibiotic residues

The presence of antibiotic residues in milk can influence several conditions within the production chain. Among them, the main ones are:

Mastitis treatment 

Mastitis is an inflammation of the udder caused by a variety of microbes, mainly bacteria, gaining access to the interior of the mammary gland. In production properties, the microorganisms that cause mastitis are a big problem for these producers, since they are quite common.

To treat this condition, antibiotics are prescribed to these cattle by veterinary professionals who monitor the herd. However, the big issue is that the lack of mastitis control in the herd will lead to the excessive administration of antibiotics in many cows at the same time.

In this sense, it is obvious that residues of these antimicrobials can be found in expressed milk.

Improper or illegal use

Antibiotic residues are even more evident when cows receive inadequate treatment, deviating from the instructions on the package insert.

Among the most inappropriate actions that occur, we can mention overdose, duration outside the recommended or dry cow treatment during lactation. All this can occur when the producer tries to treat the cows on his own, without consulting a veterinarian.

Hygiene and improper milking

It is necessary that the cleaning and sanitization of the place where the cows are treated is done correctly.

This is because it is possible to contaminate the environment with milk containing waste from cows undergoing treatment. 

For this reason, producers must be aware that the milking and disposal of milk from cows at the beginning of treatment and within the grace period for eliminating the antimicrobial does not interfere with the process of milking other animals or contaminate the milking tank. milk.

In a milking machine, the residues of a contaminated milk can contaminate the milk of other cows.

Thus, the hygiene of these equipment is of paramount importance. 

Lack of records of treated cows

Cows that are on treatment must be separated from healthy ones. 

When differentiation does not occur, either by marking these animals or changing the environment, it is possible that the professional who milks the cows accidentally removes the milk from the cows undergoing treatment.

Disrespect for grace period

The withdrawal period is a fundamental point of attention when we want to reduce antibiotic residues in milk.

This period is established in accordance with the maximum limits of antibiotic residues allowed in milk. 

Currently, those who define these values are the FAO (Food and Agriculture Organization) and the World Health Organization (WHO). 

These withdrawal periods for antibiotics are described in the package insert of the veterinary medicine, and must be respected to avoid the occurrence of residues in the milk.

Several factors can influence the length of the grace period, including:

• The dose and treatment protocol;
• The route of administration;
• The type of antibiotic;
• The product formulation. 

So, for example, antimicrobials used via intramammary administration during lactation have a rapid release, with a grace period between 2 and 6 days. In the formulations for dry cows, the release is slow, that is, the withdrawal period can be much longer. 

If you want to avoid antibiotic residues, without a doubt, the first place to pay attention and care is the farm. This basic action needs to start at the heart of the problem, using these antibiotics rationally, with advice from veterinarians.

To do this, follow these essential recommendations that we have separated so that the milk on your property is as pure and original as possible:

Follow the directions in the antibiotic package inserts 

The industries that develop veterinary drugs are very concerned and carry out very incisive tests to attest to the efficiency and effectiveness of the products.

In this sense, the leaflets are explanatory manuals that must be followed strictly, considering that this material contains essential information for the treatment. 

The producer needs to know the type of medicine that he will administer to the herd, in addition, he must verify that the following information is present in the package leaflet:

• Trade name and active ingredient of the drug; 
• Milk disposal period; 
• Recommendations regarding use and route of application;
• Recommended dosage;
• Validity;
• Registration next to the Map.

Do not use human antibiotics in animals

Antibiotics for humans do not provide information about the milk discard period. In that sense, it is wrong to try to treat animals blindly.

It is important to know that data such as dosage, recommendations for use, and route of application are elucidated in these drug inserts with a focus on humans.

Therefore, respect the particularities of each antimicrobial and use veterinary drugs for cattle in your herd. 

Separate antibiotics from dry cows from lactating cows

It is possible to classify antimicrobials into two types: for cows in the dry period and for lactating cows. So, at the time of storage, it is important to separate these two classes, so as not to confuse and administer antibiotics from dry cows to lactating ones.

This concern is due to the fact that drugs for dry cows have a higher concentration.

In this way, it is possible to find more antibiotic residues in the milk of a lactating cow that has received the wrong treatment. 

Apply the antibiotic correctly

Intramammary applications are quite delicate and must be performed by a trained professional.

The great existing risk is due to the possibility of inoculation of other microorganisms present in the environment.

So, in order not to further complicate the existing framework, the procedure should be done as follows: 

• Clean the end of the teat with cotton soaked in alcohol;
• Use a sterile cannula;
• Insert only two to three millimeters of the cannula into the teat; 
• Apply the antimicrobial.

After the procedure performed on the mammary gland, it is extremely important to disinfect the teat by immersion with an effective disinfectant. 

Caution: Never use the same cannula to treat several cows. This can lead to new infections with pathogens from the environment.

Identify all treated cows. 

Cows that have received treatment need to be separated from healthy cows to avoid contamination of the entire herd's milk.

Imagine losing an entire tank of milk due to contamination by two or three cows that are undergoing treatment? 

It wouldn't be a good scenario for the producer, would it? Therefore, the farm management needs to have control of these cows under treatment.

Notes should be made that include:

• The name or number of the treated cow;
• The date of treatment, and the reason for treatment;
• Antimicrobial used;
• Antibiotic administrator;
• Milk discard period.

All cows undergoing treatment must be identified to avoid mistakes during milking.

Discard the milk from the four breast quarters

Even if the antibiotic was applied to only one quart, the milk from all four quarts should be discarded. That's because the antibiotic is absorbed into the bloodstream, being secreted by all of them. 

Do not change the recommended dosage or route of application

The dosage and route of application are specified in the leaflet and must be strictly followed.

If there is a need to increase the treatment period, it is extremely important to seek guidance from the Veterinarian responsible for milk disposal. 

As for the route of administration, each formulation has a specific mode of absorption. Therefore, do not try to macerate a tablet orally to place it directly on the bovine's injured skin, the pharmacological effects will not be greater that way.



Always respect the recommendations to be successful in the treatment of cattle.

The antimicrobials are absorbed by the animal's bloodstream and whenever these drugs are administered, it is possible to find traces of their elimination in the milk until it is completely debugged.

Even in the face of this reality, with good practices in the production chain, it is possible to avoid these antibiotic residues in milk.

In this article, you can see what actions to take to have a product with higher quality and free of contamination.

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