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36 | INTERNATIONAL AQUAFEED | January-February 2015

EXPERT T●PIC

Welcome to Expert Topic. Each issue will take an in-depth look at a particular species and how its feed is managed.

SHRIMPEXPERT TOPIC

The evolution of modern shrimp farming by Malachi Stone, International Aquafeed

Although marine shrimp farming has been practised in many Asian countries for at least a hundred years, it is only in the

past decade or so that it has really become an economically important industry. In the past, shrimp were viewed only as a second-ary crop. Generally, fry were accidentally washed by the tide into coastal paddy fields and brackish fishponds. Trapped there, they were simply allowed to grow to a decent size then captured and sold. The supply of fry would depend entirely on fluctuations in the wild population. No efforts were made to control predators or competitors for food and space, and there was no artificial feeding system. The young shrimp were thus left to fend entirely for themselves. Even the water they were living in was usually too shallow to protect them adequately from freak changes in weather conditions. For all these reasons the yields were somewhat haphazard. Even in a good year, a farmer could only expect to harvest between 100 and 300kg per hectare.

Then the market changed. Farmers real-ised that the shrimp in their paddy fields were beginning to sell for more than the rice

itself. So they simply converted their fields and fishponds into shrimp farms.

Where used, modern shrimp farming techniques have addressed many of the fail-ings of the traditional system. Wherever pos-sible, the farmer has taken active control of the situation rather than leaving it to chance. There is a greater density of shrimp in the pools, because more seawater – and thus, more fry - has been pumped in. The pools have been dug deeper, providing a more constant microclimate: the more water over the shrimps’ heads, the greater the protec-tion from environmental fluctuations.

One problem remains, however.

Expansion of the industry is still constrained by an inconsistent supply of fry, which still depends on captures from wild stocks. So far only one species of shrimp, Penaeus chinensis, is able to complete its entire breeding cycle in captivity.

Shrimp in culture start out feeding on the algae and aquatic plants that occur naturally in their pools. However, as they get larger a supplement is usually needed. Like lobsters, they are often fed on trash fish, often mixed with rice bran. Other feeds vary from: crushed snails, mussel and clam meat, household leftovers and even large pieces of cowhide suspended in the water for them to feed on.

January-February 2015 | INTERNATIONAL AQUAFEED | 37

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1

2

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 man-aged 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 solutionsFor 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 fruitionDr Eckel was one of the first European feed additive producers who

expanded its business to aquaculture and aquafeed industries. The suc-cess 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 addi-tives 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 sea-water 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 gainThe 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 pre-sume 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 challengeSurvival rates did not differ between groups in the growth experi-

ments. 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 respec-tively) compared to shrimp in the control group (64 percent) when challenged with a virulent strain of Vibrio parahaemolyticus.

Researchers marvel at immunological effectsDuring the experiments, special emphasis was put on immunologi-

Figure 1: Protective feed additives are a building block of healthy shrimp farming

1by Tilman Wilke, Susanne Kirwan (Dr. Eckel GmbH, Niederzissen, Germany), and Niti Chuchird, Hataitip Niyamosatha (Aquaculture Business Research Center, Kasetsart University, Bangkok, Thailand)

38 | INTERNATIONAL AQUAFEED | January-February 2015

EXPERT T●PIC

cal 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 signifi-cantly 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 chal-lenged animals they discovered a spectacular histopathological pattern: Shrimp from the treatment group had less cell necrosis in the hepato-pancreas 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 investigationAlthough 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 anti-oxidant, 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 pro-duction 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, what makes them suitable for extrusion and micro diet formulation. And they work in low concentrations – leaving enough space for nutritional ingredients.

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Figure 2: Histology of the hepatopancreas of control shrimps showing 30 percent cell necrosis (left) compared to the

hepatopancreas of shrimp of group fed 400ppm of Dr. Eckel phytogenic feed additive showing 5 percent cell necrosis (right).

Magnification 500x, Hematoxylin and eosin stain. (Copyright: Niti Churchid, Kasetsart University)

January-February 2015 | INTERNATIONAL AQUAFEED | 39

EXPERT T●PIC

2

With unique expertise in the use of clay and algae, Olmix has developed a new product aimed at

the improvement of shrimp performance through increased digestive enzyme activity and better digestive balance vital in prevent-ing Vibrio. The solution lies in improving gut health.

Shrimp farming started to develop in the 1970s. In 2012, world shrimp produc-tion was over 4 million tonnes and more than 50 percent of the shrimp eaten in the world today comes from aquaculture. South East Asia and China represent the largest and the most productive shrimp production areas, accounting for 80 percent of world production. Although shrimp production has boomed over the last few decades, farmers have to face a variety of issues to ensure their production. Shrimp are very sensitive animals and many disease outbreaks have occurred in the past, such as white spot viral disease in 1994-1995 in south East Asia, and some are still ongoing, such as Early Mortality in Shrimp syndrome, hitting stocks across South East Asia since 2010.

One of the most important of these dis-eases is Vibriosis, which kills shrimp at all stages of the production cycle. More than ten Vibrio spe-cies have been reported pathogenic for shrimp.

Though Vibrio bacteria are part of the natural flora and culture environment of shrimp, Vibriosis can occur in a context of imbalanced environment and may cause total mortality of the reared shrimp. During the last two decades, mass mortality incidents in growout ponds and hatcheries due to Vibrio were widely reported. Among the different Vibrio species, Vibrio harveyi is considered one of the most important shrimp pathogens.

With very good management practices, it is possible to limit the Vibrio problem. In order to have complete protection against the pathogen, it is important to find ways to prevent shrimp being contaminated by Vibrio. Antibiotics and chemotherapy are often used to manage disease outbreaks. However, these methods have limits, such as environmental hazards or the spread of antibiotic-resistant

bacteria. Another way to prevent Vibrio disease is improved gut health. The gut is one of the most important conduits used by Vibrio to infect shrimp. It is possible to favour the natural defences of the gut by preserving its natural balance to avoid Vibrio development and toxicity.

While there is scientific evidence show-ing the benefits of clays in the prevention or treatment of digestive problems and in the protection of the gut mucosa, much less is known about their capacity to improve feed efficiency. Yet the improvement of the digestibility of feed is an integral property of clays. The mechanisms involved are thought to be multiple (Reichardt, 2008). The domi-nant hypothesis described in the literature is that clays slow down the transit of feed in the intestine, so the time for digestion is

by Jean Peignon, aqua technical service, Olmix, Vietnam

Growth performance Control MFeed+ 0.1 percent

Variation over control

MFeed+ 0.2 percent

Variation over control

Average initial weight, g/ind 6.32 ± 0.13 6.32 ± 0.13 / 6.32 ± 0.13 /Average final weight, g/ind 12.4 ± 0.8 13.09 ± 1.1 +5.6% 13.44 ± 0.1 +8.4%

Specific growth rate, percent/d 1.22 ± 0.1 1.31 ± 0.1 +7.4% 1.34 ± 0.1 +9.8%Total feed consumption, g/ind 8.66 ± 0.64 8.21 ± 0.92 / 8.52 ± 0.77 /

Feed Conversion Ratio 1.42 ± 0.1 1.22* ± 0.09 -14.1% 1.23* ± 0.1 -13.4 percent* p-value < 0.05

Health performance Control MFeed+ 0.1 percent

Variation over control

MFeed+ 0.2 percent

Variation over control

Vibrio at 60 days, x104 CFU/g - - - - -In hepatopancreas 3.07 ± 0.39 2.83 ± 0.31 -7.8% 1.17** ± 0.13 -61.9%

In the intestine 1.67 ± 0.30 1.58 ± 0.25 -5.4% 1.13 ± 0.12 -32.3%Survival rate, percent 67.2

± 4.3878.4** ± 4.56

+16.7% 82.4** ± 3.58 +22.6%

** p-value < 0.01

40 | INTERNATIONAL AQUAFEED | January-February 2015

EXPERT T●PIC

increased, hence a better digestibility of feed and increased nutrient uptake.

Nevertheless, it seems that the action of clays to enhance feed digestion in the intestine also involves other mechanisms. Reichardt (2008) and Habold et al (2009) both report the ability of clays to favor the contact between enzymes and nutrients and therefore to improve the rate of digestion of the feed. Indeed, digestive enzymes need to be in contact with their substrate in order for hydrolysis to occur. The physico-chemical interactions of the enzymes with clay particles seem to enhance the contact between the digestive enzymes and the feed, making clays a good supporting matrix for enzymes and acting as a meeting point for them to be in contact with their substrate. Indeed, Cabezas et al (1991) demonstrated that clay-enzyme complexes are formed at enteric pH values. These active stable complexes are resistant to proteolysis and increase the amount of active digestive enzymes in the intestine, thus improving nutrient digestibility.

In the same way, Habold et al (2009) observed higher pancreatic lipase activity in rats supplemented with Kaolinite; Xia et al (2004) showed an increase in small intestinal digestive enzyme activity in broilers supple-mented with Montmorillonite; and Paolo et al (1999) observed an increase in protein and energy retention coefficients for growing pigs

supplemented with clay. Some studies also suggest that the increased activity of enzymes in contact with clay comes not only from their stabilisation, but also from the presence of cofactors in the clay (Reichardt, 2008; Habold

et al, 2009). Cofactors are defined as thermo-stable non-protein compounds that form the active portion of an enzyme system. In other words, cofactors are helper molecules required for enzymes to be active. They can be organic

January-February 2015 | INTERNATIONAL AQUAFEED | 41

EXPERT T●PIC

After adding VIUSID® aqua to each feed intake throughout the production process, the following results were:

A specific product to improve productivity of aquaculture

www.catalysisagrovet.com

or inorganic, most commonly vitamins in the first case and metallic ions in the latter.

Clays are layered mineral materials, com-posed of a succession of aluminum and silicium based sheets, the order of which varies depending on the type of clay. In Montmorillonite, several metallic ions replace some aluminum and silicium ions in the struc-ture. Known as the substitution phenom-enon, this event provides montmorillonite with part of its physico-chemical reactiv-ity. Moreover, the presence of metallic ions may contribute to the activation of some enzymes, through their action of cofactors (Niederhoffer, 2000). In this way, copper is known to activate lipase and phospho-lipase A (Jondreville et al, 2002) and zinc is a required cofactor of carboxypetidase (Williams, 1960), to mention only a couple of examples.

The combination of the matrix support provided by the clay and the cofactor effect coming from the metallic ions present in its structure can be referred to as biocatalysis: the improvement of performance of a bio-chemical reaction through the action of an external compound, a biocatalyst. Due to a large variety of clay minerals, one can imagine that all clays do not have the same potential for biocatalysis depending on their type, their purity, their source or their treatment. As such, clay structure can be modified and asso-

ciated with other materials in order to unlock its biocatalytic properties. Such technology has been developed by Olmix group (France) in the course of its research conducted on seaweeds and clays. The micronized form allows a fine dispersion of the product in the intestine, providing many sites of enzymatic digestive reaction with more easily accessible metal ions.

Moreover, it benefits from a synergy between clay and seaweeds in the pro-cess of biocatalysis, as seaweeds bring in many diverse metallic ions, sometimes absent in the feed, which are required cofactors for the activation of several enzymes. This unique combination of seaweeds and clay makes it a unique tool to boost enzyme activity through the action of biocatalysis. MFeed+, the only product benefiting from this new technology, has proven its effi-cacy in several studies. In one, MFeed+ was tested on shrimp by researchers at Kasetsart University (Thailand). The aim of the study was to evaluate the effect of MFeed+ feed supplementation on digestive and growth performance of Penaeus vannamei.

375 shrimp (6.3±0.2g weight) were dis-tributed in fifteen 500 L glass tanks contain-ing 25 shrimp each. After a 7-day period of acclimatization during which all shrimp were fed the basal diet, tanks were randomly allot-ted to one of three treatments (5 replicates

per treatment): one control, fed the basal diet and two MFeed+ groups, for which the basal diet was supplemented with 0.1 percent or 0.2 percent MFeed+. Growth performance parameters and mortality were recorded during the 60 days of supplemen-tation. Vibrio bacteria were counted in the hepatopancreas and the intestine at 60 days as a marker of digestive health. The shrimp were fed three times a day to satisfaction. The feed amount was adjusted daily based on the feeding ability of the shrimp. Uneaten feed was siphoned out of the tank 2 hours after feeding. Water used in the experiment was seawater, with salinity adjusted to 12-15 ppt. The water in the tanks was aerated with air stone and exchanged every 2-3 days at the rate of 10-30 percent volume depending on its visible quality.

Feed Conversion Ratio was greatly improved in groups receiving MFeed+. As a consequence, average final weight and specific growth rate of shrimp supplemented with MFeed+ tended to be higher. Moreover, bet-ter digestive performance helped to improve the digestive status of the shrimp, as dem-onstrated by a lower Vibrio count in the hepatopancreas and the intestine and the improved survival rate of the juveniles. This study highlighted the potential of MFeed+ to improve digestive and zootechnical perfor-mance of shrimp.

42 | INTERNATIONAL AQUAFEED | January-February 2015

EXPERT T●PIC