Yes, it is true that in Canada, the milk is discarded while a cow is on antibiotics. The reason for buying organic milk is the quality of the milk. A four year study in England comparing milk from organiccally raised cow vs conventional ( side by side) found the organic milk had 60% more antioxidants. Organic cows are not vanccinatied and never receive antibiotics, which produces a healthier cow. I have a friend who saved $14,000 a year in vet bills when he switched from conventional to organic dairy farming. While many Canadian farmers have small farms and treat their cows well including letting them out of the barn, organic famrers go even further to make sure their cows are grass-fed as much as posible. Grass fed cows produce milk with hgher levels of essential fatty acids, CLA, Vitamin E and carentenoids. More importantly, organic milk is pasteurized at a lower temperature so less nutrients are lost and it tastes better. Be sure to consume whole milk so you get the essential fatty acids and Vitmain A and E all in the form we need as humans. There is very little calorie difference between whole milk and skin and these nutrients are far more important than saving a few calories.

http://www.ncl.ac.uk/press.office/press.release/item/?ref=1211878767