Ask an Agro – Week of March 8/2018

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Are there antibiotics in the milk we drink?
Just like humans, cows can get sick. Sometimes, antibiotics are used to treat illnesses in individual cows. In congruence with Canadian dairy practices, when this happens, the cow’s milk is collected separately and discarded until the antibiotics have cleared her system.

In Canada, there is zero tolerance for antibiotics in milk, whether conventional or organic, and producers can face heavy penalties. Every time milk is picked up from producers, samples are sent to an independent lab for tests, including somatic cell counts and antibiotic residues. If antibiotics are found in the milk, the entire truckload is discarded.

If there were antibiotics in milk, we wouldn’t have delicious products like cheese and yogurt, as antibiotics disrupt the fermentation processes essential to make these products.

Dairy systems use somatic cell count tests internationally to detect the cellular content of milk. In the context of cows, a somatic cell is any live cell found in the udder. The maximum allowed SCC limit in Canada is 400,000 cells per millilitre.

From July to December 2017, the Canadian farm average was about 209,000 cells per milliliter — just over half the maximum allowable limit — although this data excludes the provinces of Saskatchewan and Newfoundland and Labrador. To put this in perspective, one cubic millimetre of human blood contains four to six million red blood cells.

Does milk contain pus?
We’ve all heard claims that there is pus in milk. However, this too is a myth. The cells found in normal milk through SCC tests are primarily live cells in the mammary gland. Pus, on the other hand, is a collection of dead white blood cells, dead skin cells and bacteria, and its presence in milk would not pass quality testing. Any harmful bacteria in milk are destroyed by pasteurization.

Canadian Quality Milk is an on-farm monitoring program run by Dairy Farmers of Canada that ensures food safety and overall best management practices across the nation. The program tracks the testing and storage of milk, animal transport and the use of on-farm medication. Dairy Farmers of Canada also conducts on-farm welfare assessments to ensure that each farm meets a high standard of animal health and care.

If you’re curious to learn more, visit the Rayner Dairy Research and Teaching Facility on campus or go to for virtual tours of dairy barns across Canada.

Ask an Agro is a monthly column where students from the College of Agriculture and Bioreserouces answer queries about the Canadian food system. You can send questions to or

Jessica Jackson,  Janelle Smith, and Ashly Dyck

  • Davis

    I can’t say enough how glad I am to see science based information regarding food safety and agriculture in our university newspaper! #agmorethanever