How to reduce the diseases of cultured grouper

With the breakthrough of artificial reproduction and culture technology of grouper, the scale of grouper culture continues to expand, especially the industrial circulating water culture model has become an important support for the development of northern grouper culture industry in recent years. however, the large-scale outbreak of grouper diseases has also become a major obstacle to the development of industrial culture of grouper. At present, the more effective measure to reduce the outbreak of fossil grouper disease in factories is to strengthen the prevention and control of nerve necrosis virus, parasites and bacteria from the aspects of disinfection of fertilized eggs, cutting off the transmission of virus, monitoring of culture water environment, culture management, daily operation and so on. In addition, there is no effective drug and other means that can fundamentally cure viral neuronecrosis.

At present, the phenomenon of disease outbreaks in grouper factory farming is also widespread in the livestock and poultry breeding industry, which not only causes huge economic losses and even threatens the safety of human life. The continuous struggle against livestock and poultry diseases has made people realize that if the healthy living environment of animals is not guaranteed, too high density, the activities of animals are limited, and the environment becomes extremely bad, it will lead to the decline of animal body resistance. to create conditions for the epidemic and spread of the disease. Therefore, in line with the development of modern livestock and poultry breeding industry, the concept of animal welfare arises at the historic moment. Animal welfare, literally translated from the word "animal welfare", came into being in the early 1960s, aiming at the problems in intensive production, such as the increase of diseases, body damage, mortality, abnormal behavior and so on. The purpose of this paper is to appeal to ensure the normal production of livestock and poultry while paying full attention to the welfare of livestock and poultry. Improve the welfare level in the process of livestock and poultry production. To define the ideal state of animal welfare, the World Association of farmed Animal Welfare (FAWC) has established a standard framework of "five exemptions", namely: freedom from hunger and thirst, freedom from discomfort, freedom from pain, injury and disease, freedom from fear and sadness, and freedom to express normal behavior. Concerned about the welfare status of fish, fish belong to relatively higher vertebrates in aquatic animals. Studies have proved that fish have the ability to perceive, cope with and remember the external uncomfortable environment. However, there is still some controversy in the scientific community as to whether fish and other aquaculture animals have the ability to experience pain, fear and sadness. Therefore, at present, the evaluation of aquaculture animal welfare is mainly focused on the physiological health index of aquaculture animals. As for farmed fish, the general biological characteristics such as apparent characteristics, growth status, mortality, health status, stress response and behavior can reflect the welfare status of fish. Related studies have confirmed that when the welfare of farmed fish is affected by environmental and biological stress, the physiological response of fish will go through three stages. In the first stage, catecholamines are released from chromaffin tissue and the hypothalamic-pituitary-interrenal tissue axis (HPI) is activated to stimulate the secretion of steroid corticosteroids and release into the circulatory system. The second stage is a series of physiological and biochemical changes mediated by various hormones produced in the first stage. It involves the regulation of almost all physiological functions related to fish life activities, such as respiration, metabolism, acid-base and osmotic pressure balance, immune activity and cellular response. The third stage: on the basis of the physiological and biochemical changes in the second stage, farmed fish can not adapt to the environment or other pressures, resulting in slow growth, decreased disease resistance, poor fecundity, low mobility and even morphological changes. In recent years, scientists in Europe and the United States have made exploratory studies on the culture welfare of fish such as rainbow trout, Sparidae and flounder. It was found that culture conditions such as different water exchange rates, different stocking densities and different ozone concentrations had effects on apparent traits (mainly body surface and fin damage), deformity rate, mortality, behavioral characteristics (mainly swimming, feeding, competition, etc.), blood indexes (mainly cortisol and immune factors), neuroendocrine (mainly growth hormone, neurotransmitters, etc.) of cultured fish. So researchers and aquaculture industry gradually use these related indicators to measure the level of fish welfare. Sick tiger spot in the fish culture industry, it is generally believed that the links that can affect animal welfare include environmental factors such as facilities and equipment, aquaculture water and biological factors such as daily operation and management, fishing and transportation, bait supply and so on. Therefore, how to avoid the adverse consequences caused by long-term and repeated stress from the source of environment and biology has become the central goal of the welfare pursuit of fish culture. it is embodied in artificially providing a culture environment for farmed fish that basically conforms to their biological habits and reducing stress, and ensuring adequate nutritional feed. And take measures beneficial to the self-welfare of fish in the process of disease prevention, culture management, fishing, transportation and processing, in order to provide high quality and safe aquatic products for the society. In recent years, some phenomena have seriously hindered the healthy development of the industry, such as disease outbreak, serious residual food of fish fry, high deformity rate of fry, slow development of fry, abnormal body color of commercial fish and so on. The root causes are closely related to the reduction of immunity, abnormal behavior, stress stimulation and other factors related to the animal welfare level of grouper caused by excessive culture density, lack of nutrition, deterioration of water quality and improper operation. The decline of welfare level of grouper caused by the change (deterioration) of ammonia nitrogen, pH, dissolved oxygen, temperature, salinity, flow velocity and flow pattern in aquaculture water environment is often shown as weakening movement ability, incomplete body surface characteristics, dull body color, slow growth, inactive feeding, reduced survival rate and so on. The phenomenon of flatulence of grouper after stress floats on the water surface in recent years, a number of successful industrial culture enterprises of grouper have begun to realize the importance of providing a stable water environment for grouper aquaculture, and have introduced circulating water equipment, water quality monitoring equipment, Internet of things and other new technologies and facilities to ensure a suitable growth environment, and achieved good results. The culture density in culture management is also an important factor related to the animal welfare of grouper. Too high culture density will affect the normal growth of grouper, increase the probability of residual food and the risk of disease outbreak and production operation; while the culture density is too low, it not only reduces the resource utilization but also is not conducive to the formation of grouper population behavior. Only appropriate culture density can reduce the damage caused by physical contact, reduce the chances of mutual interference and competition during feeding, and reduce the spread of diseases such as viruses, bacteria and parasites. In addition, daily operations such as seedling division, pond division, artificial disturbance stress and operation mode will also reduce the welfare level of grouper, resulting in the decline of seedling immunity, abnormal development, abnormal body color and even mass death. in order to change this situation, we must improve the skills and quality of employees, inculcate the welfare culture concept of being kind to breeding objects, and formulate and strictly implement reasonable culture regulations. Uncomfortable operation methods, methods and safeguard conditions of fishing, transportation and processing will also affect the animal welfare status of grouper, such as body surface characteristics, body color, meat quality and even survival rate. in the downstream of grouper culture industry, how to take measures and technical measures to improve the welfare and product quality of farmed fish according to the consumption habits of domestic consumers In order to achieve the goal of providing consumers with high-quality and safe protein will be an important symbol of the high-end of the grouper farming industry in the future. All in all, grouper culture in China is changing from extensive small workshop culture mode to intensive industrial culture mode, no matter in terms of facilities and equipment, or from the aspects of water quality monitoring, culture management, feed and nutrition, operation standards and other aspects have the conditions for welfare culture, many under the conditions of extensive and semi-extensive culture. The problems that affect the yield and quality of cultured grouper, such as broken fins, bites, abnormal body color, slow growth, abnormal development and swollen swim bladder caused by the decrease of animal welfare level, can also be solved by upgrading the culture model. In the future, there are still many key technical problems to be solved in how to improve the level of welfare culture in the industrial culture of grouper, which involves many fields, such as fish biology, fish culture, environmental ecology, system engineering, information technology and so on. I believe that with the joint efforts of people from all walks of life A healthy and sustainable development of grouper culture that can ensure animal welfare and product quality will eventually be realized in the near future.