It is believed that the continuous excessive and disorderly use of antibiotic products in animal feed will lead to the rapid emergence of drug-resistant strains and the embarrassing situation of ineffective drug use. Therefore, the resistance of antibiotics and the residues of some drugs in food have caused people's confusion.
Plant extract products are recognized as "safe, efficient, stable and controllable" feed additives, and gradually become a new economic growth point for green, environmentally friendly and safe animal food production and feed industry. Plant essential oil has antibacterial, insecticidal, immune enhancement and growth promotion effects, which provides reference for green and healthy aquaculture of aquatic animals.
Application of Plant Essential Oil in Aquaculture
1, prevention and treatment of bacterial diseases of cultured fish with essential oil
Bacteria are the main pathogens causing aquatic animal diseases, accounting for 57.6% of biological diseases. Common pathogens are Vibrio, Edwardsiella, Aeromonas and Streptococcus. In recent years, due to the drug resistance and residues of antibiotic products, it has brought challenges to the prevention and control of aquatic animal diseases, and it is urgent to develop new antibiotic substitutes to prevent and control aquatic animal bacterial diseases.
The antibacterial activity of plant essential oil against pathogenic bacteria of aquatic animals has been confirmed, and it can effectively inhibit harmful bacteria such as Edwardsiella tarda and Vibrio.
2. The prevention of plant essential oil to aquaculture fish bloom.
Hydromycetes are the general name of oomycetes and fungi microorganisms of Hydromycetes, which are widely distributed in fresh water areas. Among them, Hydromycetes, Spirillus and Myxomycetes are the most harmful to cultured fish. Aquaculture is one of the main pathogens that plague cultured fish, and it is easy to infect hatched fish eggs, injured fry and adult fish.
Because the traditional products that inhibit mold are basically antibiotics, how to use safe and efficient alternative drugs to control water mold is an urgent problem in the field of aquaculture and aquatic product quality and safety, and plant essential oil is a potential choice. Plant essential oil has obvious damage to the cell wall and cell membrane of mold spores and hyphae, and can inhibit spore germination and hyphae growth. For example, fish eggs are easily infected by water mold in the early stage of embryonic development, and water mold parasitic on dead eggs is easy to infect live eggs, which seriously affects the hatching rate.
It is found that an essential oil has a good inhibitory effect on parasitic water mold, and bark essential oil and leaf essential oil have a significant inhibitory effect on water mold isolated from Atlantic salmon.
3. Plant essential oil to prevent parasites in cultured fish.
Parasitic disease is a common and frequently-occurring disease in fishery diseases, and it is also difficult to control. Therefore, pesticides play an important role in the prevention and treatment of fish diseases, accounting for about 1/3 of aquatic drugs.
In the past, chemical insecticides were used to control fish parasitic diseases. At present, there are two kinds of fishery insecticides in China, namely, internal medicine including chlorpheniramine hydrochloride, albendazole and praziquantel, and external medicine including zinc sulfate, trichlorfon and beta-cypermethrin. However, with the passage of time, drug resistance also appeared. At the same time, these drugs have accumulated residues on cultured animals, which can cause quality problems of aquatic products.
As a safe and effective new insect repellent, plant essential oil has strong cell permeability. For example, it is found that azadirachtin, a plant essential oil, has strong cell permeability and has a good killing effect on rotifers and goldfish lice. Recent studies have found that many plant essential oils are used as aquatic pesticides, which can effectively repel parasites of aquatic animals.
4. Effect of plant essential oil on immune function of cultured fish.
Immunoenhancers, also known as immunostimulants, can improve the nonspecific or specific immune function of the body and enhance the body's ability to resist diseases and infections.
At present, plant-derived immune enhancers such as bile acid, astragalus polysaccharide and β -glucan have been successfully applied to the prevention and treatment of aquatic animal diseases, and plant essential oil is also one of the potential immune enhancers for aquatic animals.
Streptococcus is the main pathogen that harms tilapia, among which Streptococcus Dolphinus can cause high mortality of tilapia in a short time. The results showed that the activities of lysozyme, peroxidase and phagocyte in tilapia serum were significantly improved after adding plant essential oil to the feed for a period of time, and the survival rate of tilapia infected with Streptococcus Dolphinus was significantly improved.
A mixture of essential oils and synthetic chemical pesticides.
The mixture of plant essential oil and synthetic chemical pesticides has at least four aspects:
Function: synergistic, transdermal absorption, covering up the bad smell of pesticides.
It can significantly improve the insecticidal effect, prolong the duration, increase the insecticidal spectrum, reduce the dosage of pesticides and reduce the production cost.
Pyrethroid insecticides, such as cypermethrin, deltamethrin and fenvalerate, are widely used to control parasitic diseases of aquatic animals, but the effect is getting worse due to the emergence of drug resistance. The use of plant essential oil can be used as its synergist.
An effective way to improve the efficacy of chemical insecticides is to add transdermal absorption enhancers. At present, azone is the most widely used, which has a strong penetration promoting effect, so that the effective components of pesticides can quickly enter the parasite, thus improving its killing rate. The results show that the oil of Artemisia argyi and eucalyptus leaves have strong permeation promoting effect because of their small molecular structure, and their transdermal absorption effect is better than azone. Experiments also show that they can penetrate the cysts of melons and spores.
At the same time, the application of essential oil can achieve the dual purposes of insecticidal and antibacterial, so it has broad development prospects. With people's increasing attention to food safety and the increasingly serious problem of antibiotics, plant extracts will play a more important role as high-quality and safe aquatic feed additives or aquatic drugs. ?