As best I can figure that one's in a box of books. If I ever get a chance to unpack them all, it's one of the books I'm looking for. I'll favorite your comment here, and try to get back to you. :)

This is not the reference, but something I just found on google books about the efficiency of dairy cows: https://www.google.com/books/edition/Farming_the_Business_Ma...

(responding to request for the reference for the dairy cow as an efficient converter of grass on rocky hillsides).