Zhejiang Province is a national economic province, and Hangzhou is a provincial capital of Zhejiang Province. It is known as the "land of fish and rice, the home of silk." At present, provincial and municipal people of all walks of life and fisheries administrative departments have recognized this problem and have referred it to the agenda to prepare for the establishment of the “Aquatic Quality Monitoring Centerâ€. Its purpose is to formulate standards that require water The products are produced, processed and sold in accordance with standards. The quality of the aquatic products is monitored and tested. The Ningbo City of Zhejiang has taken the lead in establishing the “Aquatic Product Quality Monitoring Centerâ€. The Shanghai Bureau of Quality and Technical Supervision has already established “safety. “Local standards for high-quality aquatic products†are the trend of the times. Hangzhou City tests the meat (pork), vegetables, and tofu in daily consumer products, and conducts sampling inspections by specialized agencies. The same applies to aquatic products. Healthy breeding has become imminent, but it is limited to the special situation of the aquaculture industry in the city, namely state-owned units, collective units, and more specialized households for breeding, from breeding species, aquaculture forms, breeding cycles, aquaculture techniques, breeding environment The average weight difference is large, and the previous quality problems of aquatic products have not been given corresponding attention. There is also a trial, summarization, and promotion process for the implementation of Kang culture, which must recognize the urgency of providing pollution-free food and change production techniques to meet product standards. The problem is described as follows, I hope to play an important role.
First, seed problems
Seedlings are the basis of the aquaculture industry. The emergence of a good breeding species can raise an industry upsurge (such as turtles, turtles, river crabs, giant prawn, shrimp, prawns, etc.). On the contrary, a poor breed will give the industry To a greater loss. Variety refers to a species with good germplasm gene, no degradation, strong disease resistance, rapid growth, high feed utilization, good meat quality, certain genetic stability, and should be derived from the original species. Generation - improved species. In order to make the cultivated species healthy and less harmful and reduce the use of drugs, the residues of various drugs and heavy metal ions can be minimized. However, breeding of seedlings often takes a long time and costs a lot and needs to be completed by specialized scientific research institutes. Hangzhou has invested some effort in this area. The following measures are mainly used to improve the quality of seedlings:
1. Crossbreeding Breeding of superior varieties or strains by means of artificial crossbreeding, and directional breeding of species with fast growth, strong resistance to disease and resistance to stress, for the majority of farmers to breed. This is one of the most important breeding methods in China. Such as silver squid, Feng Yu and so on.
2. Bioengineering techniques are obtained through gynogenetic development, pedigree breeding, combined with multilineage crossbreeding, or by artificial induction (temperature, pressure, biological factors) to double the chromosomes of aquatic product species. For example, Jian 鲤 (purple purpurea and Yuanjiang 鲤 as original parent), unisexual tilapia grade. For example, the engineering triploid (triploid) and triploid species have the characteristics of fast growth and large individuals. Now people know more and more clearly about DNA, and their molecular breeding techniques will gradually improve. We believe that in the near future there will be more and more healthy varieties that are cultivated using DNA technology.
3. The production of disease-free seedlings is becoming more and more intensive. Today, the diseases of farmed species are also increasing, especially viral diseases. Therefore, in the cultivation of conventional seedlings, the promotion of “healthy seedlings†and “viral-free or sterile seedlings†is to strictly select the parents throughout the seedling raising process and strictly control the number of bacterial viruses and other harmful organisms in the water, so as to minimize the The degree is conducive to future breeding. For example, many shrimps are now cultivated using this method, such as SPF without specific virus. In the future, it will also increase its disease resistance from the genetic level.
4. Genetic characteristics of aquaculture germplasm The current aquaculture industry in China tests only the introduction, development and domestication of cultured species. With the development of the aquaculture industry, due to the long-term inbreeding and the genetic characteristics of many good varieties have changed, they must be tested regularly to ensure that they have a good idea. The developed countries, especially the United States, have done relatively well. China has done less work in this area and has a certain degree of blindness in aquaculture production.
5. The rejuvenation of good germplasm is the rejuvenation of germplasm on large-scale farmed species. The current main approach is to introduce the origin or natural germplasm on a regular basis to improve the decline in the growth characteristics of the culture due to the long cultivation time. Variations in individuals become smaller. This problem exists in many species cultivated in our province, such as the mixing of shrimp and crab strains and inbreeding, so that the specifications of commodities are generally smaller than the original in the same culture conditions, and many fishes also have this phenomenon. In the future, we will solve problems by applying improved seed and artificial breeding.
6. Strictly controlling blind introductions The increase in the number of farmed species in China in recent years is greater than that at that time and in that country. This has also brought serious consequences. Regardless of whether it is introduced from abroad or from outside the province (including trans-regional), strict quarantine (especially the former) must be carried out to clarify the original diseases of the district and the status of the disease and the disease caused by the species. The impact of the pathogenic flora and the evaluation of the hazards to the major local economical culture species; the identification of the impact of the introduction of the species on ecological balance and germplasm resources will be introduced. Blind introduction has caused a lot of damage to our original breeding and introduced varieties, especially the diseases in the breeding of shrimp, crab, and crab. The “Administrative Measures on Aquatic Seed Production†issued by the Ministry of Agriculture should be strictly implemented.
Second, environmental issues
Aquaculture water environment is becoming more and more serious with the development of industry. This is a worldwide environmental problem, including direct water pollution, land pollution and atmospheric pollution, but it will eventually pollute the water environment. As for the development of aquaculture, its own biological pollution is also increasing. Deterioration of environmental conditions will surely increase the diseases of cultured species and increase the use of drugs by farmers. The higher the accumulation of heavy metals and pesticides, the higher the residue of antibiotics, thus affecting the quality of products. The main measures to improve the aquaculture water environment are:
1. Selection of site and water source The excavation of Xintang must consider the choice of site. There are not many ponds newly excavated after the release of grain in Zhejiang Province. It is also necessary to consider this issue (only the new fish ponds were added in 2001 in Hangzhou area. Thousands of acres). Open ponds must be selected from sources that have sufficient water, fresh water, and little or no pollution. To understand the situation of industrial pollution and pesticide pollution around the year, if necessary, carry out water quality tests to meet the fishery water quality standards in China.
2. The removal of excessive silt is particularly important for old ponds. Silt is often the site for the proliferation of pathogens, and excessive silt can cause excessive oxygen consumption in the breeding process, and can also cause outbreaks in disease seasons. Generally only about 20 centimeters of mud can be left.
3, the bottom of the improvement
(1) In addition to removing excess silt every year, it is best to allow them to dry in the winter, killing a large number of harmful pathogens and their spores, spores, resting eggs, etc. through freezing and sun exposure, reducing the number of onset of the coming year. And after cracking the substrate, air and soil can be fully contacted, the organic matter in the substrate can be fully oxidized, minerals can be mineralized into inorganic salts, and can become the nutrient source of food organisms in the pond in the coming year.
(2) Before stocking each year, use sufficient amount of quicklime to fully mix with the sludge. A stable and slightly alkaline water environment that can maintain the pH of the water will be conducive to the breeding of beneficial microorganisms and reduce the disease. Second, the bottom silt can be loosened. , increase the permeability.
4. Clear ponds Clear ponds can be dried at the end of the year or before stocking in the coming year. The main purpose is to remove the wild fish, shrimp and pathogens in the pond, which will help the survival rate of the culture and reduce the incidence of the breeding process.
5, water treatment
(1) Chemical treatment Many high-intensity cultures are equipped with water treatment tanks to avoid large-scale disease outbreaks in culture. This means that the cited sources of water are pre-sterilized to kill pathogens and ensure that the water added to the pool is not With pathogens, reduce the occurrence of diseases and improve the survival rate. For example, the pretreatment of shrimp in high-level pond culture.
(2) Biological treatment mainly applies and controls the growth of beneficial microbial communities. When the beneficial microorganisms multiply, the growth of pathogenic bacteria and harmful bacteria will be inhibited and the occurrence of diseases will be reduced. In addition, beneficial bacteria can decompose organic substances under aerobic conditions and reduce self-pollution in the breeding process. Biological treatment of higher levels of biological rotation, bio-packaging, etc., in industrial or recirculating aquaculture, etc.; lower level of treatment is the regular addition of beneficial microorganisms, such as PSB, digestive bacteria, viable bacteria, etc., in general culture ponds.
(3) Physical treatment is mainly through pre-sterilization or filtration of influent water by UV or ozone.
6. Simulating the natural ecological environment In the cultured water body, as many species as possible are added to habitats, hidden sites and activities. For example, additional nets for three-dimensional culture of green shrimp and hanging nets for the cultivation of greenhouse turtles are all aimed at increasing the sheltered sites for farmed species; planting aquatic plants in shrimp and crab farming can increase their hidden sites to reduce mutual mistreatment and absorb Some organic matter and other nutrients improve the water quality; the food table in the soft-shelled turtle farm has the function of drying and back. This is to increase the survival rate and benefit in the breeding, but at the same time, it can reduce the occurrence of diseases by simulating the natural ecological environment.
Bone screws, also known as fracture fixation screws, are commonly used in clinical practice to fix orthopedic implants.
Bone screws are usually used to fix internal fractures or dislocations by directly screing into two different bone blocks or fixing an internal implant such as a bone plate to achieve fracture fixation, position the bone and promote its healing. Bone screws are used in a wide range of areas, including the shoulder, elbow, hip, knee, spine, etc. For example, pedicle screw systems are used for spinal fusion, and compression bone screws are commonly used for foot and ankle surgery or fixation of other fractures under pressure. Similar to traditional mechanical screws, the main structures of bone screws also include nail cap, nail body, and nail tip. Screws can be used to fix bone plates or bone fragments. When used for the former, they are called plate screws, and when used for the latter (to prevent the collapse of bone fragments), they are called positional screws. The latter can be inserted into the plate holes, and can be placed on the bone alone (also known as compression screws). Compression screws can be used to increase interfragment pressure.
(1) The screw cap
The screw cap has three main functions: the first is to optimize the force. The protruding cap makes the contact area between the screw and bone larger, increases the load area, optimizes the local force at the screw insertion site, and reduces the risk of bone rupture caused by excessive stress. The second is the positioning effect. The prominent cap makes the bone nail can only be screwed into a certain depth to prevent the whole bone nail from being screwed into the bone completely. The third function is to provide the position of force application by rotating the force groove at the cap to move the bone nail forward and drive it into the bone. Now, the force groove is mostly inner hexagonal, which does not require axial force to maintain the actuator in the center position and is suitable for a wider range of fractures.
(2) Screw the body
The size of the nail body determines the strength and fatigue resistance of the bone nail. The larger the diameter of the nail body, the stronger the strength will be, and the corresponding fatigue resistance will be better. In addition to the diameter of the nail body, the pitch and tooth depth of the screw body thread are also the key parameters of the nail body design. Different thread design has an important effect on the pressure and occlusal performance of the screw.
(3) Screw tip
Tapping is the process of phalangeal nail cutting thread in the bone. According to the shape of the nail tip, the bone nail can be divided into self-tapping nail and non-self-tapping nail. The nail tip of the self-tapping nail is sharper and can be directly screwed into the bone without pre-drilling. Usually, self-tapping screws are used for Cancellous bone, and the bone is compressed when the screw is inserted, so as to increase the bone density of the occlusal part locally and enhance the occlusal effect. However, when inserting screws in Cortical bone, the screw channel is generally pre-punched, and then the bone screw is screwed. Usually, the self-tapping screw is not directly used to prevent the bone screw from being stuck or damaged because the cortical bone is too hard.
Bone Screw,Cancellous Screw,screws in bone,Cortical Screw
Jiangsu Aomed Ortho Medical Technology Co.,Ltd , https://www.medthofixation.com