Analysis on the cause and control of eel disease

Under certain temperature and humidity conditions, many molds can multiply in feed raw materials or finished feed, and produce some carcinogenic, cytotoxic or neurotoxic mycotoxins, among which aflatoxin exists widely and has high toxicity. Aflatoxin can cause liver and kidney damage in eel and has carcinogenic and lethal effect, but the half lethal dose (LD50) of eel has not been reported. Eel farmers generally do not feed moldy feed because of the high price of eel. However, when batching, feed factories should pay attention to the raw materials used not to be contaminated by Aspergillus flavus. Pesticides, polychlorinated biphenyls, crude oil and hydrocarbons are caused by water pollution caused by pesticide residues in farmland, discharge from chemical plants, leakage from oil refineries and so on. These substances are very toxic to eels and can cause hepatomegaly and abnormal development of eels. Carcinogenic and lethal effects. Among them, organophosphorus and organochlorine pesticides can destroy the normal physiological function of eel nervous system, inhibit the transmission of nerve energy and block the transport of ions. Although the direct toxic effect of organochlorine pesticides on eels is not as obvious as organophosphorus pesticides, it is more stable than organophosphorus pesticides and can accumulate in eels, causing serious hidden dangers.

Heavy metals mainly refer to mercury, lead, zinc, cadmium, nickel and so on. there are two kinds of harm of heavy metals to eel: exotoxin and endotoxic. the exotoxin combines with the mucus secreted by Gill and body surface to form a protein complex, which covers the whole Gill and body surface and fills the space of Gill lamin. it makes it difficult for the normal activity of the Gill filament, and the eel suffocates to death. Endotoxicity is that heavy metal ions enter the eel through the gills and body surface and combine with the hydrogen sulfide groups in the catalytic active parts of the main enzymes in the body to form insoluble sulfates, thus inhibiting the activity of enzymes, hindering the metabolism of the body and causing eel death.

Therefore, when choosing the water for raising eel, we should pay attention to the analysis of water quality and try to choose the water source that is not polluted. At the same time, it is necessary to protect the water environment and strengthen the whole people's awareness of environmental protection.

Fish meal, the main raw material of eel feed, will decompose protein during transportation and storage, resulting in a series of toxins, such as histamine, putrescine, cadaverine, tyramine, alachlor, etc., which do great harm to fish. Histamine is the decomposition product of histidine, which is a kind of amine substance formed by the removal of hydroxyl groups by histamine dehydrogenase in Proteus Mogen, histamine Achromobacter and other bacteria. Eel ingestion of a certain amount of histamine will cause poisoning. Therefore, the freshness of fishmeal is very important to the quality of eel feed and the growth of eel. Histamine content and volatile base nitrogen (VBN) can be used to measure the freshness of fishmeal. The mass concentration of histamine of fishmeal with good freshness is 100mg/ cubic decimeter, VBN < 60 × 0.00001m / m.