Aqua News
Can Asian Freshwater aqua feeds rise to the challenge? By Pedro Encarnação, Biomin
T
he 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 carps (Cyprinidae) 71.1 percent. Other important fresh water 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 carps) 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 2 million tonnes. This growth in fresh water fish production was triggered by the intensification of the farming process, successful farming of new species, but most of all, by the improvements in feed technology and the rapid increase on the use of extruded feeds. These improved floating feeds, with better water stability, nutrient availability and control of feed intake, allowed the 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 on 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 constrain for the development of the industry. Feed formulations, feed quality and feeding practices used for the production of fresh water species around Asia, reflects the use 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
Table 1: Recommended crude protein (CP) levels in commercial feeds according to fish size (NRC, 2011). Species
<20 g
20200 g
200 -600 g
600 -1500 g
Channel catfish
44
36
32
32
Common carp
45
38
32
28
Nile tilapia
40
34
30
28
Table 2: Current observed crude protein (CP) levels in commercial feeds according to fish size. Species
<20 g
20-200 g
200-600 g
600-1500 g
Pangasius
38-32
32-28
28-26
26-20
Nile tilapia
36-32
30-26
26-22
22-18
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 feed usage and poor animal performance and increase 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 fresh water feeds across Asia and the repor ted nutrient requirements published in the latest NRC book on 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).
8 | INTERNATIONAL AQUAFEED | November-December 2014
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 under standing of nutrient and energy utilisation may allow fish nutritionists, 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 acids requirements, 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. 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