Original: Due to the relatively lower level of proteins in vegetable matter, herbivore manure has a milder smell than the dung of carnivores or omnivores - for example, elephant dung is practically odorless.
Simplified: Due to the relatively lower level of proteins in grasses, which herbivores eat, cattle manure has a milder smell than the dung of carnivores - for example, elephant dung is practically odorless.