Adding amino acids to feed has been widely adopted. Generally, the content of lysine and methionine in plant feeds based on cereals and soybean meal is relatively low, which can not meet the needs of animals. Adding amino acids can greatly save the amount of protein, reduce feeding costs, and improve animal production efficiency.The protein in animal products comes from the protein in the feed. The lack of feed ingredients, especially the lack of protein feed is the main factor restricting the development of animal husbandry. The use of amino acids in feed opens up other protein resources than conventional protein, and opens a way to resolve the contradiction between the development of animal husbandry and the lack of protein feed.