A method of promoting or improving the feed efficiency and the muscle to fat ratio livestock animal by administering to the animal a therapeutically effective amount of a pure or substantially pure RR-enantiomer of ractopamine. Also disclosed are animal feed preparations and compositions and pharmaceutical preparations capable of increasing lean meat deposition in an animal or for improving lean meat to fat ratio in an animal or for promoting or improving the growth of an animal or for improving the feed efficiency of an animal, the feed preparation, compositions and pharmaceutical preparations including a therapeutically effective amount of a pure or substantially pure RR-enantiomer of ractopamine.