Looking over the list of released games, I can't think of any that have a cow jumping over the moon. The closest I can think of is the conversion of Popeye, with the big moon in the background. I've never played it, so I don't know if there's a cow jumping over it at some point.
http://www.videogamehouse.net/popeye.html
Of course, it could have been an educational game and you were too young to know the difference...