Why don't my beefalo produce much manure anymore?

Solution 1:

Looks like we have an answer, straight from the beefalo's mouth, as it were:

Beefalo not producing manure

Ah, talking with the designers, this is actually a tuning change that we put in.

The Beefalo will now only produce manure when you are in the general vicinity of them. This is to prevent people from stumbling across Beefalo herds with huge amounts of manure sitting on the ground.