Asia has been the main aquaculture producer for the last two decades and produces the 92% of the total world aquaculture products. South East Asia produced 22.5 million tons of aquaculture products in the mid-2010s, which accounts the 22% of the total world production. Estimation of the production for 2020 in South East Asia is of around 30 million tonnes, based on the previous data, together with the global annual growth rate of the sector (~5.8%).

Indonesia is the main aquaculture producer in Southeast Asia, contributing to 50% of the region’s production, followed by Vietnam, the Philippines and Thailand. Likewise, Indonesia is the regional leader in the culture in brackish water and mariculture, especially in the shrimp production. Regarding culture in fresh water, Vietnam is the main aquaculture producer, followed by Indonesia. The most common freshwater species in the region include tilapia, carp and catfish.

The Southeast Asian aquaculture industry aims to establish itself as an important source of animal protein for human consumption in an overpopulated region, as well as to supply other markets through exportation. In order to optimize the efficiency of the farms, maintain the competitiveness of their products and allow their export to other countries, it is important to understand and solve the challenges that aquaculture faces in the region.

AQUACULTURE CHALLENGES IN SOUTH EAST ASIA AND SOLUTIONS

The aquaculture industry in Southeast Asia is currently facing challenges related to the microbiological and nutritional quality of the feed, its digestibility and utilisation, as well as several infectious challenges.

QUALITY AND UTILISATION OF THE FEED

A combined approach should be performed to improve the utilisation of the diet, which should assess:

• The nutritional quality and composition of the diet.
• The health of the digestive system of the animals.

Regarding the quality and composition of the feed, the factors of great relevance are the inclusion of plant ingredients and their digestibility, as well as the conservation of the properties of the ingredients. Furthermore, this should be combined with a proper gut health, which would allow to maximize the growth efficiency and maintain the competitiveness in the market.

DIET COMPOSITION

The rate of inclusion of fish meal in aquaculture feed has decreased in the recent decades due to its price, availability and environmental impact, as this product is obtained from fishing. The continuous growth of aquaculture worldwide has led to the use of alternative protein sources, even in naturally carnivorous species, to avoid the depletion of natural resources.

Nowadays, the inclusion of plant protein is common, and oilseeds are frequently used. Addition of plant protein to the aquaculture feed allows to reduce costs and ensure the supply of high-quality and relatively stable feed to aquaculture producers. Despite this, it is a challenge for fishes whose digestive tract is not used to this type of ingredient and lacks endogenous enzymes to degrade this kind of proteins.

Therefore, a combined strategy should be planned to increase the digestibility of plant protein, which should be based on the use of exogenous enzymes, such as subtilisin, together with the administration of acidifying products. The use of acidifying products decreases the pH of the digestive tract and, thus, a greater transformation of pepsinogen to pepsin occurs. A better activity of endogenous enzymes, such as pepsin, as well as exogenous ones, improves the digestibility of this type of protein.

GUT HEALTH

In addition, to optimize the use of the diet, animals should have a proper integrity of the intestinal mucosa and a balanced intestinal flora. The use of intestinal conditioner pronutrients is recommended for this purpose. Pronutrients are active molecules of plant origin, which have a metagenetic mechanism of action based on the stimulation of functional protein synthesis.

Intestinal conditioner pronutrients act on enterocytes, optimizing different intestinal functions, such as the rate of epithelial regeneration, the metabolism of enterocytes and the paracellular permeability (improvement of tight junctions). Thanks to these pronutrients, a physiological improvement of the integrity and activity of the intestinal mucosa is achieved, the proliferation and invasion of pathogens is controlled, and the absorption of nutrients is enhanced. The inclusion at 1% of intestinal conditioner pronutrients in the diet of tilapia fingerlings has been shown to be effective in increasing growth up to 16% and improving batch uniformity.

QUALITY OF THE FEED

Another essential factor to ensure farm productivity is the administration of high-quality feed. Feed preservatives and antioxidants are ingredients that should be included in the formulation to maintain the nutritional quality of the feed and preserve its properties.

Feed preservatives prevent feed spoilage caused by microorganisms, such as fungi and bacteria, which use the energy and protein of the diet to grow and may cause digestive or systemic disease once ingested by animals. The use of organic acids as feed preservatives is a usual strategy. Organic acids have short time fungistatic and bacteriostatic effect and may have a corrosive effect in the facilities.

At the same time, the inclusion of antioxidants in the feed prevents oxidative alterations of different nutrients in the diet, such as fats, fish meals and fat-soluble vitamins. Synthetic antioxidants, such as BHT or ethoxyquin, have a potential carcinogenic effect and can accumulate in the fatty tissue of animals. Because of this fact, their use has been limited in many countries, such as Japan or the European Union, usual importers of aquaculture products from Southeast Asia.

Therefore, it is necessary to search for natural solutions with a preservative and antioxidant effect that are safe and effective, such as products based on cimenol ring.

The cimenol ring is an active molecule derived from plant extracts that, unlike organic acids, has bactericidal and fungicidal action against the main pathogens that colonize feed. This molecule pierces the fungal and bacterial membrane and alters its cellular metabolism. Cimenol ring-based products have a strong antioxidant activity and broad-spectrum, long-lasting antimicrobial function (effective up to six months), which has been demonstrated in multiple in vivo and in vitro trials. Unlike organic acids and synthetic antioxidants, cimenol ring-based products have low reactivity, long duration and have no corrosive effect nor toxicity, they are safe for handling, they are intended for all species and production stages and they do not accumulate in the organism of the animal.

INFECTIOUS CHALLENGES

The limitations established in the use of chemical products, such as antibiotics to control the main infectious challenges in aquaculture, make prevention essential to maintain the performance of aquaculture farms. Preventive plans in aquaculture should be based on a combined approach, using several tools that will allow the animal to show its maximum productive potential with the lowest risk.

Vaccination plans are a widely used strategy, although there are diseases for which this tool is not yet properly developed. In addition, it should be noted that aquaculture species are very susceptible to stressful situations due to environmental conditions, transportation, or handling, which may lead to immunosuppression of the animals.

Therefore, it is essential to establish, as mentioned before, combined strategies that include: a management plan, to ensure proper control of the environment and reduce animal handling, and the use of natural solutions based on immunostimulant pronutrients.

Immunostimulant pronutrients are active molecules of plant origin that, through their metagenetic action, physiologically increase the synthesis of proteins related to the function of the innate and acquired immune system of the animals. The use of immune booster pronutrients, ensures a correct immune status of the animals, a better immune response after vaccination, greater protection against stress and disease situations, and a reduction in the overall mortality of the batch. The inclusion of immunostimulant pronutrients at 0.4% in the diet of tilapia fingerlings showed a positive effect on production parameters and immunological status, and a decrease of 30% in the mortality rate. In addition, the inclusion of this solution reduces the use of antibiotics, thus it also reduces water contamination and the appearance of resistances both in fish and in humans.

CONCLUSIONS

Aquaculture in Southeast Asia is a sector in constant growth and development and has a great impact worldwide. In order to optimize the efficiency and competitiveness of its products, ensure the supply to the growing regional population and favor their export to other countries, it is essential to assess the challenges faced by the aquaculture industry and the available tools to fight these challenges.

The current challenges faced by the aquaculture industry are the feed microbiological and nutritional quality, its digestibility and utilisation, as well as several infectious challenges. Therefore, it can be highlighted that:

• The use of fishmeal as a protein source for aquaculture diets is not economically nor environmentally sustainable. Hence, the use of plant origin ingredients as an alternative protein source has increased. As fish lack endogenous enzymes to degrade these types of components, exogenous enzymes and acidifying products should be included in the formulation to increase the digestibility of plant protein.
• An adequate intestinal integrity and a balanced intestinal flora are essential to achieve the maximum performance from the diet and the animals. Intestinal conditioner pronutrients act physiologically on the enterocytes, improving their function, and diet absorption and utilization.
• Disadvantages of chemical feed preservatives and antioxidants, such as their limited action in time or spectrum, their secondary effects and the limitations established in several countries, imply the search for natural alternatives. The use of natural compounds based on cimenol ring, with broad-spectrum and long-term antioxidant and preservative activity without any contraindication, allow to maintain the microbiological and nutritional quality of the feed.
• There are several infectious agents that can cause an outbreak in aquaculture farming. The limitations in the diagnosis and treatment, including the use of chemical products, like antibiotics, make it essential to have an adequate preventive plan that should combine biosecurity measures together with natural solutions based on immunostimulant pronutrients. Immunostimulant pronutrients will ensure a proper function of the immune system in stress conditions and in the face of potential pathogens.

To sum up, current challenges in the aquaculture of South East Asia should be controlled through a combined approach, including: assessment of the diet and the general health status of the animals, the application of preventive strategies, such as biosecurity and vaccination plans, as well as the inclusion of natural solutions based on pronutrients, to improve the physiological status of the animals, and the use of safe and effective ingredients to maintain the feed quality and to optimize its digestibility.