by Pedro Encarnação, Biomin
The Asian region is responsible for more than 91 percent of total global aquaculture production, most of it in freshwater, with China alone contributing to about 60 of global aqua production.
Freshwater fish production is dominated by the production of carp (Cyprinidae) at 71.1 percent. Other important freshwater fish species are Tilapia and recently the dramatic growth in the production of Tra catfish in Viet Nam has made this a very important species. China is by far the biggest fresh water fish producer (mainly carp) with a production of around 23 million tons a year (FAO 2012).
India is the second biggest fish producer with 3.8 millions tons of fish produced every year with major focus on Rohu. The fast development of the pangasius industry in Vietnam made this country the third biggest producer of fresh water fish in the world with a production close to two million tonnes.
This growth in fresh water fish production was triggered by the intensification of the farming process and successful farming of new species, but most of all by the improvements in feed technology and the rapid increase in the use of extruded feeds. These improved floating feeds, with better water stability, nutrient availability and control of feed intake allowed farmers to move to higher production densities and resulted in improved fish performance and better revenues, prompting rapid growth in the sector.
However, frequently the development of these commercial feeds has been done without major knowledge of the nutritional requirements and nutrient utilisation of the different target fish species. In many cases the feed formulations do not reflect the nutrient requirement of the fish, but are mainly based on assumptions from other species or follow ingredient availability and cost constraints.
In addition, this fast growth in feed production leads to more pressure on raw material availability. Which in turn makes access to quality feed ingredients a major constraint for the development of the industry. Feed formulations, feed quality and feeding practices used for the production of fresh water species around Asia reflect the use of low cost ingredients (rice bran, rice polish, cassava flour, ground nut meal, etc) with poor nutrient profiles which result in under optimal performance by the fish.
In addition, this fast growth in feed production leads to more pressure on raw material availability. Which in turn makes access to quality feed ingredients a major constraint for the development of the industry. Feed formulations, feed quality and feeding practices used for the production of fresh water species around Asia reflect the use of low cost ingredients (rice bran, rice polish, cassava flour, ground nut meal, etc) with poor nutrient profiles which result in under optimal performance by the fish.
It is important for the industry to realise that growth performance and biomass gain by a fish depends firstly on the composition of the feed used.
Feed must provide all required nutrients in a balanced way to maximise biomass gain. The role of feed manufacturers is to select a combination of ingredients to produce a formula that will contain sufficient levels of essential nutrients needed for the targeted animal species. This selection is done on the basis of chemical composition, nutritional value and cost of the different feed ingredients.
At the end a compromise between the cost of the feed and its nutritional value for the animal must be achieved. Variable quality, inconsistent nutritional content and possible contamination or adulteration of the raw material is a huge challenge for the development of consistent nutritional feeds in Asia. Strong efforts must go on understanding characteristics and limitations of feed ingredients.
Digestibility of protein and amino acids is variable and can dictate the level that each ingredient can be used. Maximum levels of inclusion of certain ingredients in the formulation should be defined to prevent harmful levels of anti-nutritional factors that can affect fish performance (mycotoxins, phytate, glucosinolates, etc).
Feed must provide all required nutrients in a balanced way to maximise biomass gain. The role of feed manufacturers is to select a combination of ingredients to produce a formula that will contain sufficient levels of essential nutrients needed for the targeted animal species. This selection is done on the basis of chemical composition, nutritional value and cost of the different feed ingredients.
At the end a compromise between the cost of the feed and its nutritional value for the animal must be achieved. Variable quality, inconsistent nutritional content and possible contamination or adulteration of the raw material is a huge challenge for the development of consistent nutritional feeds in Asia. Strong efforts must go on understanding characteristics and limitations of feed ingredients.
Digestibility of protein and amino acids is variable and can dictate the level that each ingredient can be used. Maximum levels of inclusion of certain ingredients in the formulation should be defined to prevent harmful levels of anti-nutritional factors that can affect fish performance (mycotoxins, phytate, glucosinolates, etc).
With the increase in reliance on less costly protein sources and low nutrient dense diets, we are most likely increasing the levels of raw materials with lower protein digestibility and higher amino acid imbalance, higher carbohydrate and fibre content.
This will lead to an inefficient utilisation of the nutrients in the feed resulting in an increase in feed usage, poor animal performance and increased costs to produce one kg of lean fish. This way we will not only be feeding the fish but also feeding the pond, which can be beneficial in terms of increasing natural food production in the pond, but still resulting in a less efficient process.
This will lead to an inefficient utilisation of the nutrients in the feed resulting in an increase in feed usage, poor animal performance and increased costs to produce one kg of lean fish. This way we will not only be feeding the fish but also feeding the pond, which can be beneficial in terms of increasing natural food production in the pond, but still resulting in a less efficient process.
A closer look at nutritional composition of freshwater feeds across Asia and the reported nutrient requirements published in the latest NRC book on the requirements of fish and shrimp (NRC 2011) often shows a gap between available information on fish requirements and the levels present in the feeds (Table 1 and 2). It is true that there is still a need to better establish the nutrient requirements for some of the more relevant species farmed in the Asia region, and to fully characterise and evaluate available feed ingredients for application in aqua feeds.
A better understanding of nutrient and energy utilisation may allow fish nutritionists and feed manufacturers to produce more cost effective feeds. Priority should be given to the establishment of fundamental nutritional information such as energy, protein and essential amino acid requirements and the protein: energy ratio for major farmed species.
In addition, studies on nutritional profiles and digestibility values for most feed ingredients will make it possible to do more accurate feed formulations. Focus should be given to the complete characterisation of available local feed ingredients for optimising their utilisation and make full use of local resources.
In addition, studies on nutritional profiles and digestibility values for most feed ingredients will make it possible to do more accurate feed formulations. Focus should be given to the complete characterisation of available local feed ingredients for optimising their utilisation and make full use of local resources.
When presented with more accurate nutrient and energy utilisation data the aquaculture industry in Asia may reconsider, for example, the use of low nutrient and energy density feeds (low cost feeds but not necessarily cost effective feed) for the rearing of warm water omnivorous fish (catfish, tilapia, carp). Ultimately the development of nutritional models will allow the adjustment of feed formulas to different production conditions and different production stages in fresh water species, following practices and processes well established in the salmon industry.
Based on current knowledge on nutrient requirement and nutrient utilisation, it appears that the use of deficient diets with low nutrient and energy density feeds are the main reason for the very poor feed conversion ratio (feed/gain, between 1.5 and 3) seen in most aquaculture operations.
Production cost with such feeds may not be advantageous as often perceived, when we finally take into account cost for manufacturing (e.g. extrusion), transport costs and a poor FCR often observed. The potential negative impact on the productive capacity of the rearing environment related to the high organic waste output associated with feeding low digestible nutrient density feed should also be considered.
Farmer education regarding feed and feeding practices is also a major point for the success of established improved feed formulas in the industry. Farmers need to understand that there are many ways to produce one kg of fish, and that the amount of feed required by a fish to achieve one kg weight depends primarily on the composition of the feed used. In general, a greater amount of a lower nutrient density feed will be required when compared to a higher nutrient density feed to achieve the same performance level, assuming that the two feeds are similarly balanced.
The cost of the feed ($/kg feed) will definitely be lower with lower digestible nutrients compared to higher nutrient density feeds because grains and other carbohydrate-rich feedstuffs are often cheaper than higher protein and fat feedstuffs.
However, total feed cost ($/kg fish produced) may be greater with the cheaper feed since a greater amount of that feed will be needed to achieve the same level of performance. Thus, it is important that farmers understand the benefits of using feed targeting performance and not costs.
The cost of the feed ($/kg feed) will definitely be lower with lower digestible nutrients compared to higher nutrient density feeds because grains and other carbohydrate-rich feedstuffs are often cheaper than higher protein and fat feedstuffs.
However, total feed cost ($/kg fish produced) may be greater with the cheaper feed since a greater amount of that feed will be needed to achieve the same level of performance. Thus, it is important that farmers understand the benefits of using feed targeting performance and not costs.
The use of suitable diets in aquaculture operations can significantly increase profitability by reducing feed costs, improving animal performance, maintaining water quality and minimising nutrient loads to the environment. The manufacture and use of feeds based on high quality and digestible feedstuffs is highly recommended for the aquaculture industry as long as the use of such feeds is profitable and compatible with the environment.
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