Malcom "Mal" Reynolds wrote:
does anyone have an idea of how much protein is typically found in
cow manure?

If the cow is healthy not much protein at all. There are some nitrogen
compounds though that are useful as plant nutrients. If you particularly
want to increase the nitrogen content of your soil bird manure (chicken,
turkey, pigeon, etc) has much more N compounds than cow but be careful as it
will burn your plants when fresh or if applied too heavily, whereas cow is
not likely to.

http://www.primalseeds.org/npk.htm

David