Cow shit fertilises the pasture and feeds other creatures/life in the ecosystem ultimately taking its part in creating an environment for the animal. Moreover the seeds the animal disperses will be lost if you abscond with their excretions.

There's a very real way in which a cow, say, feedsback in to the environment. It's less direct than stealing bee vomit, but still a part of the feeding cycle.

The reason I compared them though was primarily that collecting animal faeces of large mammals would probably be an overall negative (cf. bat guano) unless you artificially confined the beasts?

It seemed to me that the necessary interference in the animals natural cycles would be akin to good beekeeping (where an apiarist can prevent hive death, increase food availability, etc.).