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Aquaculture animal Of stress Response is a series of non-specific physiological reactions produced by the body's self-regulation to achieve a new dynamic balance after being stimulated by changes in the internal and external environment. The stress response intensity of different kinds of cultured animals is very different. Stress itself is not a disease, but it may become the inducement of one or more diseases (sub-health state). Therefore, in the process of aquaculture, how to enhance the anti stress ability of aquaculture organisms is the key technical requirement to improve the efficiency and efficiency of aquaculture, which must be paid attention to.
1、 Stress reaction process, influence and harm of aquaculture animals
The stress response process of aquaculture animals can be divided into three levels, namely, primary response, secondary response and tertiary response. The primary reaction is the reaction at the level of nervous and endocrine system of aquaculture animals, which is mainly manifested by the significant increase of plasma epinephrine or norepinephrine content and the significant increase of plasma cortisol content. Secondary reactions are changes in the respiratory system, cardiovascular system, immune system and other tissues and organs caused by primary reactions. The third level reaction is to lead to changes at the individual level or population level on the basis of secondary reactions, such as changes in growth rate, disease resistance, reproductive capacity and behavior. Stress reaction can reduce the feeding rate, activity, immunity, endocrine regulation disorder and survival rate of aquaculture animals, thus affecting the survival, growth, development, metabolism and reproduction of aquaculture animals, and leading to the occurrence of diseases. Many diseases occurring in the process of aquaculture are often the result of the long-term stress state of the breeding animals, which must be highly valued by the farmers.
2、 Main factors causing stress of aquaculture animals
The main factors causing stress of aquaculture animals can be divided into physical and chemical factors, biological factors and human factors. 1. Physical and chemical factors Physical and chemical factors are mainly reflected in the changes of water quality indicators, which can be caused by weather changes (rainstorm, high temperature, etc.) and breeding process. (1) Water temperature: The sudden change of water temperature can cause stress to the cultured organisms, which can cause the dysfunction of the osmotic pressure regulation of the organism. The intense stress of the cultured organisms due to the drastic change of water temperature can lead to their death. (2) Salinity: it mainly affects the osmotic pressure of cultured organisms, leading to physiological disorders of cultured organisms and endangering their lives. (3) PH: During aquaculture production, the pH range of the water body is required to be 6.5~8.5, and the optimal range is 7.5~8.0. If the optimal range is exceeded, the aquaculture organisms will be stressed and the health of the aquaculture animals will be damaged. (4) Dissolved oxygen: The low dissolved oxygen water environment will lead to the inhibition of the growth and development of aquaculture animals, and even lead to the death of the body in serious cases. Generally, the dissolved oxygen in the aquaculture pool water is required to be more than 4 mg/l. (5) Ammonia nitrogen: generally, the maximum allowable concentration of ammonia nitrogen in aquaculture water is 1.0 mg/L, and the non-ionic ammonia is 0.02 mg/L. When the concentration of ammonia nitrogen or non-ionic ammonia in the water environment is too high, the stress reaction of breeding organisms will occur, which will cause serious damage to their cells, tissues, organs and physiological activities of the body. (6) Nitrite: The farmed animals have been in the water environment with high concentration of nitrite for a long time, and their gill tissue has been damaged, their food intake has decreased, their growth has been blocked, and they may die in serious cases. The maximum allowable concentration of nitrite is 0.15 mg/l. 2. Biological factors Biological factors mainly include aquatic plants, aquatic animals, plankton and microorganisms in the aquaculture water body. The microorganisms most closely related to the diseases of farmed animals mainly include bacteria, viruses, parasites, etc., many of which are opportunistic pathogens. Their pathogenicity increases with the increase of adverse factors in the water environment, thus causing damage to the organs of farmed animals, leading to the disease of farmed animals. 3. Human factors Human factors exist in the feeding, fishing, transportation and other aspects of the breeding process, such as the overcrowding stress of breeding animals caused by excessive stocking density, the stress of feeding animals caused by randomly changing the variety, feeding method, quantity, time and location of feed, and the stress of feeding animals caused by randomly using fish drugs, fertilizers, etc, And mechanical injury caused stress of breeding animals.
3、 Aquaculture animal stress management
Aquaculture production management should be standardized in the process of aquaculture to maintain a good water environment, maintain ecological balance and eliminate stress. In breeding production, it is necessary to use fishery drugs scientifically and reasonably, prohibit the use of illegal drugs, and use high-quality feed to minimize the factors that may cause stress to breeding organisms. But what if stress occurs? Anti stress products should be used scientifically and reasonably. Anti stress products refer to the drugs that can alleviate and prevent the stress reaction of cultured animals caused by stress factors. They can be divided into stress prevention agents, adaptation promoting agents or stress relieving agents. The main function of anti stress products is to regulate the central nervous system of breeding animals, calm them, and reduce their sensitivity to stress factors; Antioxidation, scavenging reactive oxygen free radicals, and regulating the metabolic disorder of free radicals caused by stress; Regulate the abnormal metabolism of organism substances caused by stress reaction in the organism of breeding organisms. The commonly used anti stress substances in aquaculture production mainly include energy substances, vitamins, small peptides, amino acids, electrolytes, trace elements, organic acids, plant extracts, surfactants and microecological agents, such as the "whole process worry free", "VC stress free", "immune polysaccharide" and "sprinkling should stimulate" produced by Lvke Company.
Author: Qian Xinyu, Lu Qingpeng, Jin Xuexia Unit: Wuxi Fisheries College, Nanjing Agricultural University
