Complex sentence: The House Rabbit Society believes that all rabbits are valuable animals, regardless of breed purity, temperament, state of health, or whether a relationship exists with humans--the welfare of all rabbits, domestic and wild, is the organization's primary consideration.
Split into simpler sentences: The House Rabbit Society believes that all rabbits are valuable as individuals, regardless of breed purity, temperament, state of health, or relationship to humans. The welfare of all rabbits, domestic and wild, is the organization's primary consideration.