Saturday, June 11, 2016

Importance of Protecting Hepatopancreas in Shrimps










In 2015, shrimp breeding success rate is very low, there are statistics showed that the average breeding success rate in each production area is less than 30%, even if in East China areas with far ahead breeding success rate in 2014 also crashed in 2015, the success rate is less than 10% in partial areas , nearly 70% farmers lost money.

Hepatopancreas necrosis (EMS / HPNS) and White Spot Syndrome highlighted, which are difficult to prevent and control and became the most prominent risk factors for shrimp culture, leading to huge losses on shrimp culturing. In addition to disease resulting in low breeding success rate, the bad weather conditions, seed degradation, deterioration of water quality are also the main influencing factors.

1. Hepatopancreas necrosis (EMS / HPNS)

Conditioned pathogens (specific type of Vibrio parahaemolyticus ), harmful physicochemical factors and toxic algae are the direct cause of shrimp hepatopancreas necrosis, but the fundamental reason lies in the ecological farming system disorders, weak ecosystem stress resistance, failed to effectively control conditioned pathogens and toxic algae. The "unit time" farming volume exceeds the carrying capacity, toxic physicochemical factors can’t be eliminated.

It is not effective to use antibiotics when shrimp hepatopancreas necrosis occurred . Ecological prevention and control is an effective method. Anti-stress - Disinfection - Modified sediment - water culture + probiotics treated waters will receive good results. Sterilization could kill most conditioned pathogens and aging probiotics, but it’s a force in terms of shrimp, which will produce stress, so it is required Vc, calcium gluconate and bile acids to treat and ease stress response before disinfection. After disinfection treatment, to improve sediment and make water culture, accelerate the growth of nascent algae and reproduction, develop the ability of algae to eliminate nutritive salt and new probiotic to transform harmful substances. This will rebuild the efficient ecosystem to maintain a balance, so that it could effectively prevent and cure shrimp hepatopancreas necrosis.

2.Daily protection on hepatopancreas

Hepatopancreas is most important and most versatile organ for shrimp, shouldering the function of digestion and absorption, immunity, hematopoietic, detoxification and other functions. Once hepatopancreas is damaged, which will affect the growth of shrimp, seriously result in the shrimp death. Hepatopancreas is one of the most important detoxification organs for shrimp, when the shrimp goes into the rapid growth stage, more and more harmful bacteria and organic pollutants in pools rise, while shrimp hepatopancreas shoulder tremendous detoxification function, that is to transform and decompose a variety of toxic substances in the body.

The diverse functions of hepatopancreas also determines its vulnerability. Hepatopancreas not only digest and absorb the nutrients, store energy, but also fight against external invasion, expels toxins from the body. It looks like a high-load operation of a machine, any stress on outside environment, pathogens invade , overload digestion and nutritional deficiency by itself could lead to its "strike", so the protection of hepatopancreas should go throughout the whole breeding process. Do well in prevention work on hepatopancreas of shrimp disease during the breeding process, increase shrimp resistance to disease, relatively reduce the diseases, which will naturally improve the breeding.

3.The protection on hepatopancreas during liver transportation

Liver transportation is the rapid development of shrimp hepatopancreas, also the critical period of hepatopancreas function transformation, prone to cause hepatopancreas disease. Normal shrimp liver through this period will be developed into a complete, sharp angular shape, surface covered silver liver capsule, and the color gradually becomes brown or gray-green. Because of rough feeding technique by most managers, or environmental influences, liver transportation often failed to properly complete. Too many managers neglected and even no experience to check shrimp liver in the earlier liver transportation period, which leads to not timely protect liver and induce liver development. Let alone nothing is important than protecting liver in terms of the normal development of liver during the early shrimp farming. Vitamin C and bile acids working as good detoxifying substances, and together with vitamin B, are helpful for the transportation of liver with appropriate amount.

4.Protective effects of bile acids on shrimp hepatopancreas.

Su Rong Haas et al. (2001) have done a study on the anti-inflammatory and antibacterial effects of taurine and bile acid-the active ingredient of chicken bile acid , the results showed that bile acid has a strong inhibitory effect on acute and chronic inflammation, but also has a significant antibacterial effect on gram-positive bacteria, Staphylococcus aureus in vitro. Liu Yufang et al (1998) did antibacterial experiment on bile acid extracted from the gallbladder of grass carp , the results show that bile acid have a significantly inhibited effect on three gram-negative bacteria (Staphylaococcus aureus, Sarcina lutea and Bacillus subtilis)in intestinal tract in grass carp .

When bacterial diseases occurred in aquatic animals, antibiotics will be used to prevent diseases, large amounts of endotoxins are produced after bacteria killed by antibiotics. The intestine is largest pool of endotoxin in the body, endotoxin can cause intestinal mucosal edema, the necrosis of top cell in intestinal villus, increased intestinal permeability, thereby undermine the intestinal mucosal barrier function. When the mucosal barrier is destroyed, endotoxin could pass into liver via the portal vein through an intestinal mucosal barrier and harm the health of aquatic animals.

5. Bile acid is an important chemical barrier to endotoxin: 

① bile acids in the intestine could prevent endotoxin be absorbed by gut and then pass into portal vein by binding with endotoxin② bile acid acting as a detergent, has been shown that both has a direct role on both lipopolysaccharide in vitro , and bile acids may alter E. coli endotoxin in a test tube, so that it no longer causes cracking condensed, its mechanism may break down endotoxin into non-toxic endotoxin sub unit or the formation of micro-polymer. Therefore bile acids could reduce the harm of endotoxin on intestinal, liver and the whole body.

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