I got this quote from mrwakenbake's 3lb's guano guide Great source of info especially if your a dirt grower might as well be organic or whats the point of soil
Cattle Manure (0.6-0.2-0.5) - is considered "cold" manure since it is moister and less concentrated than most other animal ****. It breaks down and gives off nutrients fairly slowly. Cow **** is an especially good source of beneficial bacteria, because of the complex bovine digestive system. Cow digestion includes regurgitation (cows chew their "cud") and a series of stomachs, all evolved to help cows more fully digest grasses. Since cow manure is more fully digested, it also is less likely to become a source of weed seeds than some other manure. Depending on your location, many sources of cattle manure can be from dairy cows. Recent expansion in the use of bovine growth hormones to increase milk production certainly could become a concern for organic farmers trying to source safe cattle manures. The healthier the cow, and the healthier the cow's diet, the more nutrients its manure will carry.