In recent years, the outbreak rate of hepatobiliary syndrome in farmed fish such as grass carp, carp, crucian carp, tilapia, tuantou bream and so on has increased year by year, and the mortality rate caused by it can reach 40% to 60%. Diseased fish are susceptible to other diseases due to damage to the liver and gallbladder, and the comprehensive immune resistance of the fish is reduced, which is seriously harmful. May to October is the epidemic season for grass carp hepatobiliary syndrome, while July to September is the peak of the incidence.
Regarding the causes of hepatobiliary disease in bait-eating fish, the causes of disease should be analyzed from three aspects: disease, nutrition, and environment.
disease:
Fish will inevitably be infected by certain bacteria or viruses, basically all fish once a bacterial disease or viral disease, its own immune system will certainly be reduced, the probability of inducing hepatobiliary lesions will be greatly improved.
nourishment:
Different varieties are in different positions in the natural food chain, and their feeding intake and nutritional needs are also different, such as the emergence of matching bait, the high protein content of feed, and the imbalance between protein and energy ratio. When the amount of protein exceeds the fish body's needs, the excess protein is converted to synthesize fat in the liver and accumulates in large quantities in the liver.
environment:
Previously, we thought that the environment would not lead to lesions in the internal organs of fish, but with the continuous maturity of high-density breeding technology, the liver and gallbladder problems caused by environmental factors are being paid more and more attention!
Let's take grass carp as an example to briefly talk about the occurrence and prevention mechanism of grass carp liver and gallbladder disease.
Causes of fish hepatobiliary syndrome:
1. Feed the feed too urgently or the feed protein content is too high, and the low-quality feed with high mixed meal content is fed for a long time
2. The current situation of feeding fish in cultured water bodies is estimated inaccurately, resulting in excessive feeding for individual species or large-sized fish species
3. The feed storage time is too long or the storage environment is poor, resulting in excessive mycotoxins in the feed, and the fish will cause liver and gallbladder lesions after eating the feed.
4. Long-term abuse of antibiotics and other drugs, increasing the burden on hepatobiliary and damaging liver cells.
5. The distribution of the material table is dense or the material table is too small, and the local density is too large for a long time in a state of stress.
6. The aerator is too far from the feeding area, and the feeding area is in a local hypoxic state for a long time.
7. Breeding density is large but neglect to divert water, water quality is not good for a long time, toxic substances such as ammonia nitrogen, nitrite, hydrogen sulfide and other physical and chemical indicators exceed the standard for a long time, resulting in the long-term overload system of the fish body (liver and gallbladder), and finally lead to the collapse of the system, hepatobiliary lesions.
8. Hepatobiliary lesions carried by the disease itself.
Symptoms and time of fish prevalence:
The disease is currently the number one killer of aquaculture, due to its single occurrence of its own mortality rate is relatively low, the onset of the disease process lasts for a long time is ignored by farmers, once the liver and gallbladder problems, the immunity of the fish body declines sharply, the resistance to pathogenic microorganisms declines rapidly, most of the bacterial diseases are caused by hepatobiliary syndrome, resulting in large-scale disease, treatment is extremely troublesome. It is one of the main culprits of the increasingly incurable fish diseases.
Body surface examination
The mucus on the surface of the sick fish is significantly reduced, the hand touch is rough, the scales are easy to fall off, and some diseased fish can see the tail fin or the end of the dorsal fin is white; the surface of the dead fish has a lump of mucus all over the body, and the eyeball is prominent. It is often complicated with bacterial venereal diseases such as enteritis, gills rot, bleeding, and streptococcus.
2. Autopsy
Cut from the abdomen, the wound has only a small amount of blood flowing out, you can see a large amount of congestion in the abdomen, liver enlargement, abnormal color, there are flower liver, green liver, earth yellow liver and other symptoms; gallbladder is large, the color of the bile may become dark green, dark green, pale yellow, white, or colorless, part of the liver is fragile; the liver and the mesentery and fat adhesion; the intestine is hyperinflated, and some have intestinal bleeding symptoms.
3, the epidemic time is from March to October, and even throughout the year.
Prevention and treatment methods of fish hepatobiliary syndrome:
1, when the disease is found, the first 50% reduction, liver and gallbladder disease is mainly lipolysis, metabolic function is blocked, appropriate reduction of nutrient intake, can effectively stabilize and alleviate the disease. Then add the hepatial spirit to the Japanese material, the hepatic spirit directly acts on the fish liver, plays a detoxification and detoxification, and completely solves the role of hepatobiliary syndrome in 5 to 7 days, so that the fish liver is rosy and shiny.
2. If the water body has been frequently used before the cultivation of chemicals, the water body should be detoxified in time, the chemical drug residue should be degraded, and the harm of various toxins in the water body to the liver should be lifted.
3. When the disease and other diseases are complicated by the formation of syndromes, priority should be given to the treatment of diseases with high fatality rates, and antibiotics can be used for treatment with hepatic spirit.
4. Follow-up water quality regulation must be strengthened.
5, follow-up feed feeding must be grasped well, should not be too urgent or protein content is too high, regularly add liver protection and liver protection drugs.