Scientific pig raising questions and answers 13. What is the application of lysine and methionine in feed?

The protein in animal products comes from the protein in feed, and the lack of feed materials, especially the lack of protein feed, is the primary factor restricting the development of animal husbandry. The use of amino acids in feed opens up protein resources other than conventional protein, and opens up a way to solve the contradiction between the development of animal husbandry and the lack of protein feed. The amino acids produced by feed additive industry can easily increase the concentration of essential amino acids in feed, which not only improves the nutritional value of feed, but also obtains many other beneficial functions. This makes industrial amino acids widely used in feed industry. At present, the most widely used amino acids in feed industry are lysine, methionine and a small amount of tryptophan and threonine. L-lysine is an L-shaped optical isomer of lysine, the molecular formula is C6H14N2O5 ·HCI, the relative molecular weight is 182.65; the appearance is white or light brown crystalline powder, tasteless or with a little special smell, soluble in water, insoluble in ethanol and ether, optical activity, melting point 263264 ℃. China has established the national standard of feed additive L-lysine hydrochloride (GB8245-87). DL- methionine, also known as methionine, the molecular formula is C5H11N02S, the relative molecular weight is 149.22; the appearance is white or light yellow crystal, with a special smell of sulfide; soluble in water, dilute acid, dilute alkali, slightly soluble in ethanol, insoluble in ether, melting point 281℃ (decomposition). The content of commercial methionine is ≥ 98.5%. At present, China has not formulated a national standard as a feed additive. At present, there are four main methods for industrial production of amino acids: ① fermentation, ② chemical synthesis, ③ enzyme and chemical-enzymatic method, and ④ protein hydrolysis. Lysine and methionine are used in all kinds of livestock and poultry, but more attention is paid to methionine in poultry feed and lysine in pigs. The rational use of both is more important, and how much to use varies according to the content of raw materials and nutrients in different places. Lysine usage reference: pig weight less than 10kg, corn 65%, soybean meal 30%, lysine addition 0.50%; pig weight 10-20kg, corn 65%, soybean meal 30%, lysine addition 0.40%; pig weight 25-50kg, corn 75%, soybean meal 20%. Lysine addition 0.35%; pig weight 50-100kg, corn 80%, soybean meal 15%, lysine addition 0.20%; pregnant sows, corn 85%, soybean meal 10%, lysine addition 0.05%; lactation sows, corn 85%, soybean meal 10%, lysine addition 0.2%. Broilers add 0.1-2.5%, laying hens 0.1-0.2%, pre-laying 0.1%, late laying 0.05%. It is best to add 3-5% butter, lard, soybean oil and other fats to broiler feed. In pigs, the amount of methionine used is generally 50% of lysine, and sufficient methionine must be added to the feed of broilers and layers. If rapeseed cake and cottonseed cake are used to replace soybean meal, the addition amount of lysine must be increased by 20%, and if fish meal is used instead of soybean meal, the addition amount of lysine can be reduced by 20%. When each pig farm designs the formula, it should be flexible according to different pig breeds, different stages and different feed raw material varieties, in order to obtain better feeding benefits. (this content is extracted from the "100 questions and answers on Scientific Pig raising" edited by Yingtan Old Science and Technology Workers Association and Zhang Genkai.)