With the development of aquaculture, organic acids are increasingly used in artificial feeds. Citric acid has the advantages of being non-toxic, non-residual and the like, and it can play an important role in promoting the absorption of minerals and improving the utilization rate of feed for aquatic animals. Therefore, it has been widely used in aquaculture.
Research on citric acid: Citric acid, also known as citric acid, is a sugar-like white crystal with a lemony sour taste. It uses corn as the main raw material and is extracted and refined through a series of chemical processes such as fermentation. The obtained product is mainly anhydrous or citric acid with one part of crystal water. Citric acid has a pleasant sour taste, taste refreshing, no after-acid, safe and non-toxic, highly soluble in water, can be directly absorbed and metabolized by organisms. A large number of studies at home and abroad have proved that citric acid as a feed acidifier is the best additive. Scipionic et al. compared citric acid, fumaric acid and malic acid in feed and found that citric acid was most effective in reducing coliform and anaerobic bacteria. It is generally believed that the effect of the addition of several organic acids is citric acid>fumaric acid>calcium formate.
Citric acid's biological metabolism function Citric acid is an intermediate product of energy metabolism in the body, and has important physiological and chemical functions. It is an important medium in the process of acetyl-COA synthesizing fat, and it is also one of the important substances in the mitochondria that constitutes a chain-absorbing chain. Regulates CAMP activity and participates in a series of important reactions such as body energy, structure and enzyme protection. The role of citric acid in aquaculture feeds 1. Enhance the activity of pepsin Citric acid can reduce the pH of the feed and reduce the pH in the stomach of aquatic animals, thereby promoting the conversion of inactive pepsinogen to active pepsin . Increased acidity in the stomach can slow the emptying of the stomach, prolong the residence time of the protein in the stomach, and facilitate its digestion and absorption.
2. Promote the absorption of minerals Some mineral elements easily form insoluble salts in an alkaline environment and are extremely difficult to absorb. Citric acid can be used as a ligand to reduce the pH of the gastrointestinal tract, and it can chelate with the minerals in the aquatic feed to promote the absorption of mineral elements in the intestine. At 25°C, the complexing constants lgk of citric acid with Ca2+, Cu2+, Fe2+, Fe3+, and Zn2+ are 12.5, 14.2, 15.5, 25.0, and 11.4, respectively, and these materials form stable, biologically-effective bids. The compounds so as to promote their absorption and retention.
3. Improve feed efficiency Adding citric acid and microbial phytase can increase the utilization rate of phosphorus in plant feed, reduce the addition of inorganic phosphorus, and reduce the pollution of aquatic environment by aquatic animals through feces. Foreign scholars believe that its mechanism of action is twofold: First, to reduce the digestive pH, so as to increase the solubility and digestibility of phosphorus, and extend the time of digestive passage through the intestine to increase the absorption of total phosphorus; Second, acidified feed, Improve the feed environment. Domestic studies have suggested that citric acid can improve the utilization of phosphorus and other minerals in fish feed (fish meal). There may be two factors: first, the effect of feed acidification and dissolution; and second, the further chelation release. cation. Therefore, other acidifiers, such as inorganic acids, do not work as well as citric acid in increasing the use of minerals.
4. Promoting the growth of aquatic animals Russia's aquatic experts have found through experiments that feeding citric acid is effective without changing the basic formula of shrimp feed. If 2000mg/kg citric acid is added to the shrimp feed, the growth rate of the shrimp can be increased by at least 20%, thereby greatly reducing the feed coefficient and cost. As an additive for aquatic animal feed, citric acid can replace part of the protein as a nutrient source and increase nutrition. On the other hand, free citric acid can be directly absorbed and participate in metabolic activities in the organism, that is, participate in the tricarboxylic acid cycle, and accordingly Reduce the consumption of protein in fish and shrimp.
5. Anti-stress health effects In intensive aquaculture, changes in water temperature, inappropriate feed composition, pull-net exercise, long-distance transport, and vaccination will all lead to different degrees of stress responses in aquatic animals, and thus their production performance. Decline, resistance, or even death. Citric acid forms an energy pathway shorter than glucose, and can be used for the emergency synthesis of ATP under stress conditions, improving the body's non-specific resistance, that is, improving anti-stress ability. Studies have shown that it can be oxidized into CO2 and bicarbonate in aquatic animals, buffering the damage caused by blood alkalinity, maintaining the pH of the blood in an appropriate range, thereby avoiding or relieving respiratory alkalosis caused by high temperatures. .
6. As a fungicide for feed Add 0.5% to 5% of citric acid to the compound feed. As the pH of the feed is reduced, it can inhibit the proliferation of microorganisms and the production of toxins, reduce the loss of nutrients during storage, ensure feed quality, and reduce waste.
7. As an antioxidant synergist Citric acid and antioxidants mixed use, can improve the antioxidant effect, to better prevent or delay feed oxidation, improve the stability of compound feed and extend the storage period.
Problems to be solved The application of citric acid in aquaculture has achieved good results, but it is also necessary to solve the following problems. First, the stability of the effect: The effect of citric acid on use is not yet stable, and its mechanism is not yet clear. How to maintain the stability of feed citric acid is an important research direction in the future. The second is the optimal amount of added: the appropriate amount of citric acid added to the animal has a significant growth promoting effect. If the added amount is insufficient, the effect of reducing the pH value of the digestive tract to a suitable level cannot be achieved; however, if it is added excessively, the palatability of the feed may be reduced or the vitamin may be lost. The choice of citric acid should be combined with the type of feed, animal species and digestive physiology to determine the optimal amount of citric acid. The third is the compound acidifier: Due to the low cost of inorganic acid, plus various acids have their own advantages and disadvantages, so the development of citric acid and other acid compound acidifier is also the direction of future research. Fourth, although the acidity of citric acid is not strong, it is still possible to corrode various tools and equipment during long-term use, and preventive measures need further study.
Yellowtail,Japanese amberjack,Amberjack,Yellowtail Fish
Zhoushan Boda Aquatic Products Co.,Ltd , https://www.baida-aquatic.com