Create Rails migration with values for column

I need to change a reference for a model while updating the value and not allowing this reference to have null values.

I would like to reference Animal to Specie instead of Breed.

I will not remove Breed from this migration so I can keep it until I make sure everything works properly in production and then will run a cleanup.

Here we go:

class AddSpeciesToAnimal < ActiveRecord::Migration[5.2]
  def down
    remove_reference :animals, :specie, foreign_key: true, index: true
  end

  def up
    add_reference :animals, :specie, foreign_key: true, index: true

    Animal.find_each { |animal| animal.update!(specie: animal.breed.specie) }

    change_column_null :animals, :specie_id, false
  end
end