Soybean meal is known as the "king" of vegetable protein feed for its good nutritional properties. It is the best formula for combining with the "king" of animal protein feed, fish meal and the "king of energy feed" corn. They can learn from each other's strengths to make up for their weaknesses, so that the various amino acids in the diet are basically balanced, without additional additions. Therefore, the application of soybean meal in compound protein feed occupies a large proportion, which greatly affects the cost of livestock and poultry feed.