Some dairy cows may consume genetically modified feed such as canola meal, but genetically modified crop is regulated by the government organizations and evaluated for its safety. There is no scientific evidence showing that genetically modified feed affects milk yield or milk composition.
An important thing to note about cows eating GM food is that it does not change an animal’s (or a person’s) genetics. The cow’s milk is not GMO. A comparison can be made to diabetics taking insulin; the person does not become GMO. A dairy-related comparison is that a cow fed chocolate doesn’t make the milk that comes out of that cow chocolate milk.
The digestive system is at work by the cow’s stomach – for example, there is no “corn protein” or “wheat protein” in cow’s milk. There are only dairy proteins in milk (casein and whey), which the cow’s body builds from the amino acids.
The Canadian dairy industry respects consumer choices. Organic milk – of any brand – comes from cows that do not eat GM crops.
To conclude, there is no nutritional difference between conventional and organic milk. The process is different but the final product is the same.