A.P.
Certified organic is the only way to absolutely ensure (in legal theory) that the cows were not given antibiotics. The problem with antibiotics is that they are using the same ones we are when we're sick. This has caused such an unprecedented acceleration in microbial evolution such as has never been seen on this planet before!
Artificial growth hormones, according to all the money-making authorities, do not change the quality of the milk. However, cows that are given these hormones tend to be sick. They get infections because no cow is supposed to make that much milk. Can you imagine if you were forced to produce 3 times the milk after giving birth? Your nipples would get infected too!
Oakhurst has pledged not to use milk from treated cows. I personally have very high regard for any company who stands up to Monsanto. Non-treated cows are usually healthy. Healthy cows do not need antibiotics. Organic is overpriced because of high regulatory costs. Unfortunately, organic is now big agribusiness.
In terms of vitamins, it is always better to get them from plant sources than from supplemented food products. The whole is always better than the part and will be better utilized by the body.
By the way, as long as a cow can walk (or be kicked) into the slaughter house, it is added to the food supply. This is where the old rBGH cows are going when they can no longer produce. Get to know your local farmers - you and your family will be so much healthier for it!