Exerpt from article by Jo Robinson who writes for the New York Times. She is explaining that with organic your risk of getting sick with e-coli bacteria is much greater than with grassfed animals because it increases the acidity of the digestive tract. "The abnormal acid environment causes the e-coli to multiply and become more acid resistent. According to a recent study published in the Journal of Science, these altered bacteria are much more likely to survive the cleansing acidity of your digestive juices and make you ill.
When a ruminant is taken off of pasture and fattened on an artificial grain diet it loses its stores of vitamin E, beta carotene CLA and omega 3's. It doesn't matter whether the grain is organic or not. Feeing large amounts of any kind of grain to a grazing animal makes the meat less beneficial for human consumption. In order to have the healthiest meat, the animals need to remain on their natural diet of fresh pasture. Compared with grainfed meat, grassfed meat has four times more vitamin E, five times more cancer fighting CLA, three times more heart-friendly omega 3's, and twice as much beta carotene. It is also lower in calories, total fat, and saturated fat." She is talking about the farmers who use no pesticides or herbecides on the fields or synthetic hormones for the cattle or antibiotics in the feed.
Her 128 page book: "Why Grassfed IS Best" from the website above.
I am not a big meat eater, but never understood the diffence between organic and grass-fed animals.
They have a state to state directory of where you can get meat, poultry, eggs, cheese, etc., that is from all grass fed animals.