A recent Journal of Dairy Science research study by Mrs. Gillian Butler and coworkers from Newcastle University in the UK has received a great deal of press coverage in the UK and elsewhere. The results indicated that milk produced under UK organic standards had significantly higher levels of fat, but that there were also significant differences in the type of fat in the milk. The fats thought to be ‘beneficial’ were found to be higher in ‘organic milk.’
This result was based on milk purchased in grocery stores located in the UK, and the result is likely due to the unique ways that cows are raised/fed in the UK. Full results at http://bit.ly/f7xTgN, just click on the PDF tab. There were also significant differences in milk fat composition for season and year in this UK study.
The US data is different, however. While there is a small, though statistically different, difference in some fatty acids, analysis of milk from cows raised by organic standards, rbST-free certified or conventional methods demonstrate "...that there were no meaningful differences that would affect public health and that all milks were similar in nutritional quality and wholesomeness." The abstract is at http://bit.ly/bg4yGs, but the PDF is not available for this article without a J Dairy Science subscription.
Similarly, milk composition from various regions and seasons in the US was found to be "... remarkably consistent across geographic regions and seasons from the perspective of human dietary intake of milk fat." Again, the abstract is at http://bit.ly/exfCcU, while the PDF is not available for this article without a J Dairy Science subscription.
Dairy cattle in the US tend to be fed in a more seasonally consistent manner and are fed feeds that would tend to not amplify the results observed in the UK.
There is much misinformation regarding these studies currently in the press and on social media platforms, such as Twitter and Facebook.
You’ve got to read the primary research before you can reach conclusions. Hope that helps.