Grass-fed cows produce healthier milk than cows that eat processed grains. Milk from the grass-fed cows contain five times more cojugated linoleic acid (CLA). CLAs are unsaturated fat that not only protects the heart, it also seem to aid in weight loss.
A study of 4,000 people indicated that those who have more conjugated linoleic acids also have a lower risk of heart attack.
" 'Whole-fat milk and dairy products have gotten such a bad reputation in recent years due to their saturated fat and cholesterol contents, and now we find that CLA may be incredibly health-promoting,' Michelle McGuire, spokesperson for the journal's publisher, the American Society for Nutrition, and associate professor at Washington State University, told Reuters Health in an email. 'Whole milk is not the villain!' "
Research from Sweden and from Costa Rica also suggest that milk fat from grass-fed cows is the way to go to reduce the risk of heart attack.
http://www.reutershealth.com/archive/2010/05/28/eline/links/20100528elin003.html