Comparing conventional and organic milk,

Conventional and Organic Milk

There are so many options when you go to buy milk. Skim, whole, 2%, lactose-free, organic, and ultra-pasteurized are just a few options and that is without broaching the topic of non-dairy “milk” beverages (more soon) or alternative animal milks such as goat milk. What milk one chooses can be a very personal and polarizing decision. I remember a recent family gathering where we had seven different types of milk in the refrigerator for eleven people. We all wanted “our” milk and did not want to drink another option, even for a few days.

This post is the first of multiple articles on milk and will focus on organic and conventional milk. Future milk posts will cover the reasoning behind the daily recommended servings of dairy, recent research comparing the health effects of whole verses skim milk, as well as rice and nut-based “milk” beverages (more soon).

Dairy Milk 101

When learning about milk, there are a few basics to understand. First of all, dairy cattle, like all mammals, produce milk after giving birth. Dairy cattle typically have one calf a year in order to produce milk year round and a typical dairy cow produces 22,700 pounds or 2640 gallons of milk a year.1 Cows belong to a group of animals called ruminants, which have four stomach compartments to digest the grasses, hays and other protein or energy rich foods.2 Dairy cattle have different nutritional needs than cattle being raised for beef, and dairy cattle feed is optimized by the dairy farmer, typically with the assistance of a nutritionist, to maximize milk production.

Comparing conventional and organic dairy cattle

Conventional and organic milk come from conventional (non-organic) and organic dairy cattle, respectively. That is why, when comparing conventional and organic milk, it is important to consider the feeds, medicines, and possibly hormones being administered to the dairy cattle because what is fed to a cow can be passed through to her milk.Below is a table comparing the practices allowed during the management of organic and conventional dairy cattle.

Comparison of requirements for raising organic and conventional dairy cattle. *Antibiotic use in organic cattle causes the cattle and their milk to no longer be considered organic. **Approved parasiticide use is allowed for organic cattle, however requires a 90-day withdrawal period before milk can be collected for sale.
Comparison of requirements for raising organic and conventional dairy cattle. *Antibiotic use in organic cattle causes the cattle and their milk to no longer be considered organic. **Approved parasiticide use is allowed for organic cattle, however requires a 90-day withdrawal period before milk can be collected for sale.

Dairy Cattle Feed

Organic Feed

Organic dairy cattle must be pastured and housed on land that qualifies for organic certification.  They must have access to pasture during the entire grazing season and have at least 120 days grazing on pasture to be certified organic.4 Additionally, any feed and hay the cattle are fed must be organic. While this does not mean the feed the organic dairy cattle are eating is pesticide free, it does mean that there are no organophosphate pesticide residues or glyphosate (herbicide, trade name Roundup®) residue on the feed. Learn more about pesticide residues and the foods we eat.

Conventional Feed

There are two considerations for the hays and grains that make-up conventional dairy cattle feed: residual pesticide levels and whether the components in the feed are from genetically engineered (GMO) crops.

Residual Pesticides. Dairy cattle can come in contact with pesticides from both direct exposure around their farm environment and the feed they consume. The FDA’s Grade “A” Pasteurized Milk Ordinance suggests testing milk (either by tank load or at the dairy farm) every 6 months for the most common chlorinated hydrocarbon pesticides (such as DDT, a toxic and persistent pesticide that has not been allowed in use in the US since 1972) because of their ability to accumulate in the body.3 Though most chlorinated hydrocarbon pesticides have been banned for use in the US for decades, residues are still found periodically in milk samples.5

Dairy cattle are also exposed to a wide range of other pesticide residues through the feed they consume, and there are no routine practices in place to monitor those pesticide levels in milk. The EPA sets allowable pesticide levels, or tolerances, for individual crops, and the tolerance for a pesticide varies not only for different crops, but can also vary across different parts of a single crop. For example, the EPA tolerance for the pesticide imidacloprid in soybeans can range from 35 ppm for soybean hay to 3.5 ppm for soybean seeds.6 The tolerance levels set for hay and forage are typically higher than the tolerance levels for produce. Some pesticides ingested by dairy cattle can be passed on to their milk, and though the residual pesticides in milk are not routinely tested by the USDA, the agency periodically includes analyzing the pesticide residues in milk in its Pesticide Data Program (PDP) as a “special project.”5 The results from the available years vary widely, as shown by the graph below.

Conventional milk samples with detected pesticide residues, data from USDA PDP milk "special project."5
Conventional milk samples with detected pesticide residues, data from USDA PDP milk “special project.”5

In 2011, only 1% of the tested milk samples had any detectable pesticide residues. However, in 2005, 99% of the milk samples tested had detectable pesticide residues and 85% of the tested milk samples contained trace amounts of DDE (a metabolite of DDT). It would be a mistake to look at the 2011 test results and conclude that there has been an overall reduction in residual pesticides in milk. The most reasonable assumption is that there is a wide variance in pesticide residues in the feed dairy cattle consume. It should be noted that none of these detected pesticide residues were above the set EPA tolerances.

Feed from Genetically Engineered Crops. The majority of corn (92% USA / 81% Canada) and soy (94% USA / 62% Canada) grown in North America are genetically modified to be herbicide (typically glyphosate) tolerant and/or insect resistant (more on GMOs and glyphosate soon).7 The EPA tolerance levels for glyphosate vary greatly: non-grass animal feed has an allowable glyphosate tolerance of 400 ppm while pop corn has an allowable glyphosate tolerance of 0.1 ppm.8 Though glyphosate is the most used chemical in agriculture, it is not included on the USDA’s PDP testing program, so no data exists publicly on residual glyphosate levels in milk.9 However, 90% of soy beans were found to have residual levels of glyphosate when tested as a “special project” by the USDA in 2011.10

Medicine Approved for Dairy Cattle

Organic Dairy Cattle

The USDA guidelines for organic dairy cattle management require preventative health practices to minimize infections and infestations in the herds. However, they also provide and require treatment options in the event that a dairy cow has a life-threatening illness.

Antibiotics. If an organic dairy cow has a life threatening infection, or is suffering, antibiotics must be administered. However, the milk from the cow may not be sold or fed to organic calves, and the cow must be transferred to a non-organic dairy farm.4

Parasiticides. Three synthetic parasiticides are allowed for use in the case of health care emergencies and require a 90-day withholding period for lactating dairy cattle.4

Growth Hormones. The use of hormones to encourage growth or increase milk output is prohibited in organic dairy cattle.4

Conventional Dairy Cattle

Administration of medicine to dairy cattle is common while managing a dairy farm, with antibiotics and parasiticides as two of the most commonly administered classes of drugs. When a medicine is approved for dairy cows, a residue tolerance in milk is typically established by the FDA. Additionally, withhold periods, if applicable, are determined where milk must be discarded until the medicine residue is considered below the safe tolerance level.11

Antibiotics. Infections, such as mastitis, are common among dairy cattle and antibiotics are often administered. Some antibiotics have specific withhold periods, where the milk from the affected cow is not allowed to be sold. As an example, amoxicillin has a withhold period of 60 hours after last treatment.12 The FDA’s Grade “A” Pasteurized Milk Ordinance for requires testing of every truckload of milk for residues of the most commonly used class of antibiotics on diary farms (Beta-lactam).In the FDA’s Center for Veterinary Medicine’s 2013 Milk Drug Residue Survey, less than 1% of all tested milk samples tested positive for Beta-lactam antibiotics.13 However, not all antibiotics have withhold periods. As an example, monensin, an antibiotic that has an FDA-approved claim to “increase milk production efficiency” has no withhold requirements and is routinely mixed into dairy cattle feed.14-16 And because monensin is not a Beta-lactam antibiotic, it is not one of the antibiotics that is routinely tested for in milk.This means that there is a good possibility that conventional milk in the US may contain antibiotic residues.  And though there is no scientific evidence to date, it is possible that drinking milk containing antibiotics could kill the healthy bacteria in one’s intestinal tract enabling growth of unhealthy bacteria that is antibiotic resistant.17 Read more about antibiotic use in livestock here.

Parasiticides and Other Medicines. In addition to antibiotics, other medicines including parasiticides, non-steroidal anti-inflammatory drugs, and antihistamines are allowed for routine administration to dairy cattle and have allowable tolerance levels in milk.18 However, some of these medicines are not approved for human use. As an example, moxidectin, a parasiticide approved for use in beef and dairy cattle, has no withhold period during or after treatment.19 Because there are no routine testing requirements for medications in milk other than Beta-lactam antibiotics, there is no publicly available data on the residual levels (if any) of these medicines in milk. Not knowing whether or not you are exposed to even a low concentration of a medication is concerning, especially if it has not been approved by the FDA for human use.

Growth Hormones. The FDA approved recombinant bovine seratropin (rBST) also called recombinant bovine growth hormone (rBGH), for use in dairy cows in 1993. The genetically engineered growth hormone, trade name Posilac and created by Monsanto, was positioned as a way to increase a cow’s milk production by 10-15%.20 Now sold by Elanco, Posilac is marketed to farmers as “a reliable way to increase cash flow.”21 However, there are trade-offs with this increase in milk production. Dairy cattle treated with rBST have an increased incidence of mastitis, causing a corresponding increase in antibiotic use.17 And while consuming rBST does not affect a person directly because the human body does not recognize cow proteins, milk from rBST treated cows does contain elevated levels of insulin-like growth factor 1 (IGF-1) which is identical to human IGF-1. Though there are no studies that link consuming milk and dairy products with elevated levels of IGF-1 with adverse health outcomes, there are also no studies demonstrating their safety. And there are studies that have linked high blood levels of IGF-1 with an increased risk of developing prostate cancer in men and breast cancer in women.17

The use of rBST in dairy cattle has been banned in the European Union and Canada due to animal welfare concerns.20 However, rBST is still used in some US dairy farms and the most recent estimate by the USDA indicates that 17% of all dairy cattle in the US are treated with rBST.22 While milk produced from animals treated with rBST does not have to be labeled, milk from cows not treated with rBST can be labelled “rBST-free.”17


It is important to be informed about what dairy cattle are consuming because components of the feed, residual pesticides, and medicines consumed by dairy cattle can be passed along into their milk. Based on all of this information, Feed Them Wisely has assessed conventional and organic milk and made one of three recommendations: wise (), acceptable (), or avoid ().

Assessment of Organic and Conventional Milk
Assessment of Organic and Conventional Milk

Avoid: Conventional milk. We recommend avoiding, whenever possible, dairy products made with conventional milk that may contain rBST. Both the unknown health impact of consuming milk with higher levels of IGF-1 and concerns about the animal welfare of the cows treated with rBST warrant avoiding milk and dairy products from cows treated with rBST.

Acceptable: Conventional milk without rBST. The decision to rate conventional milk without rBST as acceptable is a little more nuanced. Milk and dairy products made with conventional milk without rBST will likely contain pesticide and medicine residues. However, these residues are almost always found to be below the EPA tolerances and are considered to be safe by the FDA. Conventional milk is probably okay if consumed infrequently or in smaller quantities (cheese, for example).

Wise: Organic milk. If you are pregnant, have young children, or are someone who consumes dairy frequently, it is wise to choose organic milk as that is the only way to ensure the milk you drink does not contain undesirable substances.


  1. USDA Economic Research Service, Livestock, Dairy, and Poultry Outlook No. (LDP-M-270), December 2016 (link)
  2. How Cows Make Milk, Dairy Australia website (link)
  3. Grade “A” Pasteurized Milk Ordinance, FDA 2011 Revision (link)
  4. USDA Guidelines for Organic Certification of Dairy Livestock (link)
  5. USDA PDP Special Projects, Milk, 1996, 1997, 1998, 2004, 2005 and 2011 (link)
  6. Electronic Code of Federal Regulations (eCFR), Imidacloprid; tolerances for residues, §180.472 (link)
  7. Non-GMO Project, GMO acreage in 2014: Corn (link), and Soy (link)
  8. Electronic Code of Federal Regulations (eCFR), Glyphosate; tolerances for residues, §180.364 (link)
  9. EPA Pesticides Industry Sales and Usage 2006 and 2007 Market Estimates, 2011. (link)
  10. USDA PDP Special Projects, Glyphosate, 2011 (link)
  11. Milk Drug Residue Sampling Survey, FDA, March 2015 (link)
  12. Amoxi-Mast website, Merck Animal Health (link)
  13. National Milk Drug Residue Data Base Fiscal Year 2013 Annual Report, Center for Veterinary Medicine, FDA, 2013 (link)
  14. Rumensin website, Elanco (link)
  15. Rumensin New Animal Drug Application (NADA Number 095-735), FDA, (link)
  16. Monenesin Medicated Dairy Cattle Feed, Type B Medicated Feed, Elanco, 2007 (link)
  17. What to Eat, Marion Nestle, 2006 (link)
  18. FDA Memoranda of Information, M-I-05-5: Tolerance and/or Safe Levels of Animal Drug Residues in Milk, 2005 (link)
  19. Cydectin website, Boehringer Ingelheim (link)
  20. Recombinant Bovine Growth Hormone, OLR Research Report, 2007 (link)
  21. Posilac website, Elanco (link)
  22. Bovine Somatotropin (bST) – Possible Increased Use of Antibiotics to Treat Mastitis in Cows October 30, 2013, FDA (link)


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