Wednesday, March 4, 2015

04/03/2015: Plant based health promoters for secure shrimp farming

by Tilman Wilke, Susanne Kirwan (Dr. Eckel GmbH, Niederzissen, Germany), and Niti Chuchird, 
Hataitip Niyamosatha (Aquaculture Business Research Center, Kasetsart University, Bangkok, Thailand)    

First published in International Aquafeed, January-February 2015

Dr Eckel, a leading supplier for research-based functional feed additives is about to launch its Shrimp product line in Thailand and South-East Asia in 2015. New research results from Thailand corroborate the strength of these future standards in plant-based health promoters.
Early Mortality Syndrome (EMS) is still a big problem in shrimp production in South-East Asia as well as in Latin America. EMS experts know that classical approaches like antibiotics and chemical disinfection are no solution: 

“Disinfectants are only good for a couple of minutes, so they are not the answer. Antibiotics are not the answer, either. The vibrios are there, and we have to keep them in check with balanced systems,” says Scott Horton. 

Centrepieces of such balanced systems are farms with strictly managed biosecurity and well-considered genetic resources and breeding practices. Another task is to strengthen the natural defence mechanism of the animals in order to cope with any kind of disease pressure. Functional feed additives are one way to fulfill this task. 

Demand for natural solutions

For several years customers and retailers in Europe have become more and more sensitive to the abundance of antibiotic drugs usage in animal production systems. Consumers and policymakers oppose unjustified use of antibiotic drugs either from an individual health perspective or from a global sustainability perspective. Shrimp farming enterprises who want to keep pace with that development have to change their practices and have to look for alternative ways to cope with disease pressure in intensive shrimp farming systems.
R&D efforts come to fruition
Dr Eckel was one of the first European feed additive producers who expanded its business to aquaculture and aquafeed industries. The success stories in livestock feed was encouragement to transfer the natural nutraceutical concepts to aquafeed applications. Hence, the target was to develop a functional feed additive that has positive effects on growth and immune defence of Pacific White Shrimp. 

After two years of research and development Dr Eckel is proud to reap the fruits of its labours. In 2014, the Dr Eckel research partners of the Aquaculture Business Research Centre at Kasetsart University in Bangkok reported a breakthrough. The tested phytogenic feed additives proved to have positive effects on growth, survival and immune response of shrimp. 

In a series of tank trial experiments at Kasetsart University the effects of dietary supplementation of phytogenic feed additives was evaluated at different inclusion rates (400 ppm and 800 ppm) on growth, survival, intestinal bacteria, immune responses and tolerance to Vibrio parahaemolyticus infection in Pacific White Shrimp (Litopenaeus vannamei). Postlarvae 12 (PL12) were kept in 500-litre tanks with seawater of 20-25 ppt salinity and controlled water temperature of 29+ 1°C. PL12 were stocked at a density of 50 PL per tank (100 PL/m2). In the growth experiment shrimp were fed for 60 days, the challenge experiment lasted 30 days, with Vibrio being added before stocking and at day 14 of the experiment. Each feeding group was carried out with four replicates.

Increased body weight gain

The Dr Eckel feed additive enhanced the growth rate of shrimp in laboratory condition in a dose-dependent manner. After 60 days of dietary administration, shrimp with 800 ppm inclusion rate showed the highest average body weight of 3.48 ± 0.18 g, followed by the 400 ppm group with 3.42 ± 0.22 g. Shrimp from the control group showed the lowest average body weight of 2.64 ± 0.43 g. These differences were statistically different at a p-level of five percent. The researchers presume that the feed additive improved digestibility of nutrients leading to higher feed efficiency and faster body weight gain.  This hypothesis is underpinned by the improved feed conversion ratio observed in the treatment groups.
Better survival rates after Vibrio challenge
Survival rates did not differ between groups in the growth experiments. However, in the challenge experiment shrimp from the group fed with Dr Eckel feed additives at 800 ppm and at 400 ppm had significantly higher survival rates (78 percent and 67 percent respectively) compared to shrimp in the control group (64 percent) when challenged with a virulent strain of Vibrio parahaemolyticus. 

Researchers marvel at immunological effects
During the experiments, special emphasis was put on immunological effects as one of the target mechanism of the novel feed additive. The tested feed additive improved shrimp immune response, which led to higher survival rates in the challenge experiment. In the course of their immunological studies the researchers measured the ratio of hemocytes cells that do phagocytosis to the total number of hemocytes. 

Phagocytosis is the central and terminal mechanism of the immune system to seek and destroy pathogenic bacteria or infected cells. The share of hemocytes that perform phagocytosis was significantly larger in the treatment group (23 percent) than in the control group (17 percent). Additionally shrimp in the treatment group had twice as much hemocytes compared to shrimp of the control group (4.4 x 106 versus 1.9 x 106 cells / ml).  

When the researchers examined the hepatopancreas of the challenged animals they discovered a spectacular histopathological pattern: Shrimp from the treatment group had less cell necrosis in the hepatopancreas compared to other groups (Figure 2). That means that the phytogenic feed additive from Dr. Eckel took a cell-protective effect in the hepatopancreas of shrimp. 

Modes of action under investigation

Although the biological effects are proven with scientific methods, the molecular pathway of these effects is still under investigation. The active ingredients in the feed additives are plant substances and plant extracts that feature highest levels of flavonoids and polyphenols. These substances are highly potent nutraceuticals that act as antioxidant, free radical scavenger, anti-inflammatory agent and immune system modulators.

Implications for shrimp farmers and shrimp feed producers

With the new shrimp-adapted versions of his natural phytogenic feed additives Dr Eckel delivers powerful tools that assure high production and low mortality in intensive shrimp production. The proven effects on growth, survival rate and immune response will make them building blocks of a sustainable and balanced shrimp farming system. 

Feed mills’ purchasers will be glad to hear that these feed additives from Dr Eckel are heat-stable and can be ground or even pulverised, making them suitable for extrusion and micro diet formulation. And they work in low concentrations – leaving enough space for nutritional ingredients.

Read the magazine HERE.

The Aquaculturists
This blog is maintained by The Aquaculturists staff and is supported by the
magazine International Aquafeed which is published by
Perendale Publishers Ltd

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