Further to previous comments regarding our bovine friends, I think having a 'Plan B' for when the beasties call your bluff is the golden rule. RSCs are particularly handy in this respect, having taken refuge on a number of recumbents in my time. Drewbhoy will probably have a fit at this sacrilege!!

Mind you, fallen orthostats do just as well, as long as they are in the 'large' category, as evidenced by my 12 Apostles experience:

http://www.themodernantiquarian.com/site/168/twelve_apostles_of_hollywood.html.

I've found in these instances that the animals seem to want to reclaim their authority over the field and are quite happy to let you off the hook when this has been made clear......