amino acids are the basic units of protein. The quality of protein in feed is mainly determined by the content of amino acids, especially the content of essential amino acids and whether the proportion of various amino acids is appropriate. Protein, which contains a large amount of essential amino acids in a proper proportion, has a high utilization rate and is a high-quality protein for pigs. Otherwise, it is a low-quality protein. The role of amino acids is mainly about the role of essential amino acids and their complementarity. Among the essential amino acids, lysine, tryptophan, methionine, cystine and threonine are the most important for pigs. Because pigs mainly feed on cereal grains, and the essential amino acids in protein contained in these cereal grains are not comprehensive, the quantity is relatively small, and the quality is poor. Long-term feeding of grain feed lacking one or several essential amino acids will seriously affect the growth and performance of pigs. If the essential amino acids lacking in feed are supplemented according to the feeding standard of pigs, so that all kinds of essential amino acids can reach a balance, the growth and production performance of pigs will be greatly improved. According to the experimental research, the daily gain of weaned piglets can be increased from 82 grams to 145 grams and 29 grams when the lysine content in the diet is increased from .45% to .65% and .85%. Reduce the feed consumption from 3.3 kg to 2.5 kg and 2.2 kg per 1 kg weight gain.

another function of amino acids is complementarity. Because the content of various essential amino acids in feed protein is very different, one feed protein contains more A amino acids and less B amino acids, while another feed protein contains less A amino acids and more B amino acids. In practical application, mixing these two kinds of feed together can complement each other and achieve the requirement of complementary balance. According to the experiment, using cottonseed cake and bean cake (meal) as protein supplementary feed for pigs in a ratio of 1∶1 is better than feeding bean cake (meal) as protein supplementary feed, because the protein of bean cake (meal) contains more lysine and tryptophan and less methionine; However, cottonseed cake contains more methionine and less lysine, so combining soybean cake (meal) and cottonseed cake can complement each other and achieve a balanced supply, thus effectively improving feed utilization efficiency and pig production performance. Therefore, in the case of bean cake (meal), cottonseed cake and peanut cake at the same time, it is best to mix them in a certain proportion and feed them to pigs, which will be much better than feeding pigs with one kind of cake protein feed alone.