This is part of what I found out when I was doing some research before I switched to organic milk. It is DISGUSTING what gets in your milk. Let me tell you, if you switch to organic milk you will not switch back. It tastes SO much better. It stays fresher in your fridge much longer, because it isn't already half rotten from the pus that is in it from the infected udders of the poor cows.
If you don't believe me, just check the dates on the organic milk in your grocery store and compare it to the dates on the regular milk. It is very common for me to find that the 1/2 gallon cartons of organic are dated to indicate they will last at least 2 weeks longer than the non-organic milk. There doesn't seem to be quite as big of a difference on the gallon cartons, don't know why that is.