The cows in The United States are fed whole corn.
Corn seems to pass through a digestive system without changing form.
Put them in stalls, side by side. In one cow s feed put whole corn, in the other cow s feed put cracked corn. Collect everything that comes out the other end of their digestive tracts. Count kernels of corn per Kg of manure. Better make it dry manure, some manure is wetter than others especially in the spring.