Improving feed efficiency does not necessarily mean reducing costs, but more likely involves getting pigs to market weight faster and gaining barn space. Various additives can be used to improve feed efficiency, with the most effective being antibiotic growth promoters followed by organic acids. Feed form can improve efficiency if feed is pelleted or if particle size is reduced, although too fine may increase ulcers. Increasing nutrient density will improve feed efficiency, and this can be done by feeding more energy or by the addition of enzymes.  Amino acid supplementation can be used create an ideal balance without wasting energy. Many co-products offer a decrease in feed costs, but they may also be able to maintain feed efficiency. When formulating diets with co-products, producers should strive to also maintain the feed efficiency.