Cannot /summon cross Dimension

I was attempting to summon a Cow into the nether from the overworld.

The command I used was:

/summon Cow 109 36 81

{Dimension:-1}

The cow was summoned but only at 109 36 81 in the Overworld.

The summoned cow kept the Dimension:-1 tag after being spawned, also after relogging in.