Application of Feed Additive Amino Acid in Aquaculture

Amino acid additives in aquatic feed mainly refer to limiting amino acids that cannot be synthesized by aquatic animals, namely lysine and methionine. The lack of limiting amino acids in aquatic feed often occurs when a large amount of plant protein feed is used. Due to the lack of lysine and methionine in most plant-based protein feeds. If the compound feed lacking lysine and methionine is supplemented with synthetic lysine and methionine to the level required by aquatic animals, the nutritional value of feed protein can be strengthened and the breeding effect can be improved. At the same time, the method of adding restrictive amino acids to improve the nutritional value of some plant feeds is also an effective way to improve economic benefits and rationally utilize feed resources.

1. The function and role of amino acids

Fish's requirement for protein is actually the requirement for amino acid, and the ratio between essential amino acid and non-essential amino acid in fish diet is roughly 40:60. Amino acids can promote the absorption of calcium by fish. According to experimental reports, adding vitamin D can increase the calcium content, but increasing the lysine content can further improve the calcium absorption of fish. The reason may be that calcium can specifically combine with protein to form calcium-binding protein (CaBP). Calcium-binding proteins will play a delivery role on the intestinal mucosa to promote calcium absorption. Calcium-binding protein contains a large amount of lysine, and if the amount of lysine is insufficient, the amount of calcium-binding protein produced is less, and the absorption of calcium is less.

Adding limiting amino acids to aquatic feed can improve the balance of amino acids, make the amino acids and protein in the feed have the highest nutritional value, and improve the digestion and utilization of feed protein. If a certain amount of lysine and methionine are added to the feed, the crude protein content in the feed can be reduced by more than 2% without affecting the feeding effect. Lysine plays a very important role in maintaining the normal growth and development of aquatic animals and the normal function of the nervous system. Lack of lysine in the feed will cause negative nitrogen effect (protein is decomposed and excreted), so that the protein in the feed cannot be fully utilized, the growth of aquatic animals is slow, and symptoms such as fatty liver and bone calcification rate will also appear. Methionine is the only sulfur-containing amino acid among the essential amino acids, which is involved in the transfer of methyl groups in aquatic animals, the synthesis of adrenaline, choline, and inositol, and the metabolism of phospholipids in the liver. Methionine can synthesize cysine, which has the function of protecting the liver and detoxifying. Therefore, methionine can promote the growth of aquatic animals and prevent the occurrence of diseases such as fatty liver and flower liver.

Studies have found that amino acids also have a food-attracting effect on fish. In addition to supplementing nitrogen sources, adding glycine and alanine to fish feed also has a special function of attracting fish schools. A large number of studies have shown that L-type amino acids are mainly active in attracting fish and crustaceans. Moreover, different amino acids have different attractant activities to the same species of fish. The same amino acid also has different attractant activities to different fish and individuals of different sizes of the same species. Some people think that this difference may be related to the differences in the smell and taste sensitivity of different fish to a certain amino acid and the difference in the molecular structure of amino acids. This difference in smell and taste sensitivity may be consistent with the difference in feeding habits. Different ready-to-eat properties have different amino acids with food-attracting activity. Herbivorous fish are the most sensitive to glutamate. Carnivorous fish are most sensitive to alanine and proline. Generally speaking, the combination of two or more amino acids has a better attractant effect than a single amino acid. There are also some amino acids that act as food-attracting inhibitors to some aquatic animals when they exist alone, but they have food-attracting activity when they are mixed with other amino acids. In addition to attracting food, amino acids can also improve the disease resistance of aquatic animals, such as tryptophan can increase the γ-globulin content of fish. Because it is not by medicine but mainly by strengthening nutrition to improve disease resistance. This has important practical significance for protecting the ecological environment and strengthening green food.

2. Amino acid feed additives commonly used in aquatic feed

Naturally occurring amino acids are mostly L-type, and D-type is rare. Synthetic mostly L-type and D-type 50% of the mixture, that racemic. L-type amino acids can be directly utilized by aquatic animals, while D-type amino acids are not easily utilized by aquatic animals. Therefore, for amino acids used in aquatic feed, L-type or DL-type should be selected. Amino acids added to aquatic feed mainly include the following types:

2.1 DL-methionine

DL-methionine is the most commonly used methionine feed additive. It is white, light yellow crystal or crystalline powder, with special smell, good fluidity, reflective, smooth hand feeling, no rough feeling. Slightly soluble in water, easily soluble in dilute hydrochloric acid, non-optical, the content is above 98%, and the potency is above 100%.

2.2 Methionine hydroxyl analogs

The hydroxy analogue of methionine is also called hydroxymethionine. It is a dark brown viscous liquid with a special smell of sulfide. The effective content is about 88%, and the potency is about 80% of that of methionine.

2.3 L-lysine hydrochloride

L-Lysine hydrochloride is the main commercial form of lysine. L-Lysine hydrochloride is white or light brown powder or granules, with special smell, slightly sweet taste, no bitter taste, easily soluble in water, insoluble in ethanol or ether, optically active, with a content of More than 98%, the effective content of L-lysine is about 78%.

2.4 L-tryptophan

L-Tryptophan is a white or light yellow crystalline powder with a slight peculiar smell, hardly soluble in water, and the effective content is above 98%. The price of tryptophan is relatively high, and it is rarely used in feed additives.

3. Application of Amino Acid Feed Additives

3.1 Rational application of amino acid additives according to the actual situation of feed formula

With the development of feed formulation technology, feed formulation has shifted from the traditional energy protein mode to the available amino acid mode. It is more scientific and reasonable to use amino acid patterns to design feed formula. In order to make the ratio of amino acids in the feed formula more balanced and reasonable, it is more convenient and necessary to use amino acid additives.

3.2 Reasonable selection of amino acid feed additives

Commercial amino acid additives mostly have a certain effective content and potency. When applying amino acid additives in practice, their effective content and potency should be converted first. For example, most feed additives of lysine are L-lysine hydrochloride, with a content of more than 98.5%. In fact, the content of L-lysine is about 78%, and the potency can be calculated as 100%. Feed additives for methionine include DL-methionine, methionine hydroxyl analogs and N-hydroxymethylmethionine calcium. The effective content of DL-methionine is more than 98%, and its potency is calculated as 100%. The potency of methionine hydroxyl analogues is calculated as 80% of pure product equal to DL-methionine.

3.3 Precautions for selecting limiting amino acids

3.3. l  It is necessary to accurately grasp the essential amino acid content of various feed materials in the compound feed.

3.3.2  Strictly control the amount of addition, any excess or deficiency of amino acid will have adverse effects.

3.3.3  When adding, firstly, the requirement of the first limiting amino acid should be met. Secondly, meet the needs of the second limiting amino acid, otherwise it will not produce good results.

3.3.4  When lysine and methionine are used as additives, they can be pre-mixed with carriers in order to make them evenly mixed in the compound feed. The ratio of amino acid to carrier is 1:4.

3.3.5  Amino acids should be properly kept during use, and should be protected from light, moisture, high temperature, and pests to avoid deterioration of amino acids during storage. It is best to use up the unsealed amino acid at one time, and if it is not used up, it should be tightly packed or sealed.

Polifar has been committed to animal nutrition research for 20 years and is a professional feed additive supplier. We provide animals with nutrients needed for growth, such as amino acids, vitamins, phosphates, trace elements. In addition, another goal of Polifar is to improve the economic benefits of farming by improving feed utilization. If you want to know which additive is suitable for your needs, please contact us sales@polifar.com.