Prevention and treatment of hepatobiliary syndrome in cultured herring

Herring is one of the four major domestic fish in China, and it is also a traditional farmed fish in China. Because of its fast growth rate, low feed coefficient, delicate meat and delicious taste, it has always been favored by people. In recent years, the cultivation of herring in Sichuan has gradually increased, but with the increase in production, the following diseases have seriously hindered the development of herring culture and dampened the enthusiasm of many herring farmers. Herring hepatobiliary syndrome is one of the most serious diseases harmful to herring culture. Once the disease occurs, it is difficult to treat, the cure rate is low, and the diseased fish are not resistant to transportation, thus causing huge economic losses to farmers. This paper gives a brief introduction to the incidence of herring hepatobiliary syndrome and the diagnosis, prevention and treatment of the disease.

I. morbidity and symptoms

The investigation found that the disease mainly occurred from May to August and lasted for a long time. Generally, it occurs when the water temperature is high, and the water temperature of the disease is mostly 22-28 ℃. Pond culture and cage culture are easy to occur, especially the herring whose body weight is more than 1 kg. The mortality rate of simple hepatobiliary syndrome is not high, mostly between 2% and 5%, but the mortality rate increases significantly after secondary bacterial infection, reaching 10% to 30%. Due to the common symptoms of bacterial disease, farmers are generally treated with antibiotics and antibacterial Chinese herbal medicine, but the effects are not satisfactory.

The lesions were mainly in the liver and gallbladder. Anatomically, the liver is often enlarged, brittle and brittle, with severe yellowing or partial yellowing, some with mottled stripes on the liver, and the gallbladder is often enlarged, some swollen to 2-3 times of the normal, and part of the gallbladder wall can be seen thinning. Bile color deepened or yellowed. Most of the diseased fish will be secondary to bacterial infection, appear body surface scales loose, shedding, part of the skin exposed, serious red skin phenomenon; at the same time, Gill swelling or decay; intestinal congestion, redness, intestinal cavity full of inflammatory exudates.

Second, etiological analysis

At present, there is no unified conclusion on the cause of the disease. Through the comprehensive analysis of the incidence and epidemiology of many clinical cases, it is found that the occurrence of the disease is related to feed factors and environmental factors.

Feed factor: at present, the herring with hepatobiliary syndrome we come into contact with are fed with compound feed, and many herring farmers use carp feed to raise herring directly, without using special feed for herring. The protein content of most carp feed is about 34%, resulting in high protein content, causing the herring to grow too fast and the liver can not bear the burden.

Environmental factors: there is often thick silt at the bottom of the aquaculture pond where the disease is common. In order to pursue the yield, the farmers increase the stocking density and accordingly increase the amount of bait. due to the increased burden of the aquaculture water, the water quality can not keep up with the regulation, which leads to the deterioration of the pond water environment, and the ammonia nitrogen and nitrite in the water quality generally exceed the standard. fish self-immunity is weakened, more vulnerable to pathogen infection, resulting in death.

III. Prevention

As the disease is mainly related to nutritional factors, 34% of carp feed can be used in the early stage of herring feeding, but when the herring reaches 500 grams per tail, the protein content in the feed should be gradually reduced. If there is no special herring feed, it can be fed with grass carp with a protein content of 28%. At ordinary times, we should pay attention to feeding and management, and don't be overfed. Due to the strong feeding ability of herring, as soon as they see this kind of herring with good feeding ability, they often increase the amount of feeding, resulting in overeating of herring. The growth rate of fish is also very fast due to overfeeding, so as to increase the interest of farmers, further increase the amount of bait, enter a vicious circle, and finally the liver of the fish can not bear the heavy load and get sick. Therefore, it is necessary to control the amount of bait, and it is appropriate for the fish to eat eight percent full, so as to control the growth rate of herring and prevent the burden of liver caused by excessive growth.

In addition, attention should be paid to the regulation of water quality at ordinary times. Microbial preparations are often used to regulate water quality, decompose ammonia nitrogen and nitrite produced by excessive feeding and fish excreta, prevent ammonia nitrogen and nitrite from exceeding the standard, make the water quality refreshing, give a good living environment for farmed varieties, and reduce the occurrence of diseases.

IV. Treatment

According to the reasons analyzed above, the following treatment principles were formulated: control feeding, protect liver and gallbladder, control secondary infection, and regulate water quality. First of all, reduce the feed protein content, gradually use 28% grass carp feed, and control the amount of feed, 70% full is more appropriate. Oral administration of liver-protecting and gallbladder-protecting drugs: take the liver-protecting drugs sold in the market, and at the same time take Vc 80mg / kg fish weight for 5 days. Control of secondary infection: take 50 mg / kg fish body weight florfenicol and other antibiotics for internal administration to kill the pathogens of secondary infection for 5 days for 7 days, while disinfecting with chlorine dioxide and other disinfectants, once every 3 days, 2 times for 3 times, the death rate is generally reduced after 7 days. In order to prevent recurrence, Sanhuang Powder, allicin and other traditional Chinese medicine can be used 7 days later, continuous use of 3-5 days, the consolidation effect is very good. After that, microbial preparations such as photosynthetic bacteria, EM bacteria and nitrifying bacteria, nitrifying bacteria and Bacillus can be used to improve water for external use to prevent death caused by water quality factors.

5. Summary

From the etiological analysis, the main cause of herring hepatobiliary syndrome is that the feed protein is too high and the feeding amount is too large, which is caused by growing too fast and increasing the burden on the liver. From our treatment experience, in the treatment of herring hepatobiliary syndrome, the control of secondary infection is very important, blindly protect the liver and gallbladder without controlling secondary infection, the effect is not good. However, it is often misdiagnosed as bacteriosis and treated blindly according to bacterial disease, which is only a temporary cure rather than a permanent cure. According to this train of thought, the number of deaths decreases temporarily after two days of medication, while the mortality rate rises again a few days later, resulting in the phenomenon that the disease has been delayed and the course of the disease has been prolonged. Therefore, in the process of herring culture, the prevention and treatment of hepatobiliary syndrome should adhere to the above principles of prevention and treatment, in order to promote the healthy and rapid development of herring culture, reduce death and reduce economic losses.