Why might an active Finnish Spitz require a higher caloric density diet than a companion German Spitz?

Answer

Due to its historical role as a bird-hunting dog

An active Finnish Spitz may need a higher caloric density to fuel its historical function as a bird-hunting dog, unlike a companion German Spitz kept mostly indoors.

Why might an active Finnish Spitz require a higher caloric density diet than a companion German Spitz?
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