FEATURE
Functional feed additives to enhance the digestive and metabolic capabilities of fish and shrimp
A
by Peter Coutteau, PhD, Sam Ceulemans and Alexander van Halteren quaculture is the fastest growing industry producing animal protein. Still, aquafeed production only represents four to five percent of global animal feed production and is fragmented over many species and countries around the globe. This lack of critical mass limits research developments, particularly for tropical species of fish and shrimp. At the same time, the young aquaculture industry suffers from several bottlenecks that must be solved to maintain its sustainable growth and satisfy growing global demands for fish and shrimp. Solving these bottlenecks requires multi-disciplinary work and combined progress on different areas including breeding programs, vaccine development, farm technology, husbandry, zonal hygiene management, and nutrition. At Nutriad, we believe that functional feed additives, powered by natural, bio-active compounds with specific functional properties, are an important component to solve these key issues. Strong fluctuations of feed ingredient prices, sometimes in combination with low market prices at the farm gate, have repeatedly affected the profitability of all bulk species, including shrimp, marine fish, trout and pangasius. As a result, optimising cost-efficiency of feed is a major issue for aquaculture producers. For carnivorous species such as salmonids, marine fish and shrimp, formulating feed using increasingly reduced levels of fishmeal and fish oil, without affecting performance nor health status under production conditions, has proven to be a challenge. The upcoming new generation of aqua feeds are using significantly lower levels of marine ingredients. This has been achieved by the use of alternative ingredients, mostly proteins and fats derived from plant crops, in combination with feed additives which enhance the digestive and metabolic capabilities of the fish and shrimp to deal with these “unnatural” ingredients in their diet.
Increased nutrient utilisation efficiency is key to achieve more cost-efficient feeds
Functional feed additives that enhance digestive and metabolic processes are crucial to make novel feed formulations work within the limitations of the digestive system of fish and shrimp.
Potential products for improving digestion and feed utilisation in fish include phytobiotic compounds, organic acids, enzymes, and natural emulsifiers. However, it is difficult to predict the functionality of many of these products for a wide range of fish species, covering carnivorous, omnivorous, and herbivorous feeding habits, marine/freshwater habitats, cold/tropical climates, and extremely different feed formulations. At Nutriad, a continuous programme of empiric screening for important aquaculture species aims at identifying promising compounds for application in aquaculture. Our research has mainly focused on compounds that are heat-stable in order to facilitate application under practical processing conditions for aquafeed. In omnivorous fish such as tilapia and catfish, digestive aids have shown interesting results to improve nutrient utilisation from cheap ingredients and improve economics of farming and filet processing. Lin & Wu (2014) demonstrated that the dietary protein level could be reduced in tilapia feeds by supplementing a feed additive capable of enhancing nutrient utilisation. Tilapia fed two percent less protein and supplemented with a digestive/ metabolic enhancer, showed even better performance in terms of growth, feed conversion ratio, protein efficiency and retention, Table 1. Performance and hepatic G6PDH activity of tilapia fed a control diet (28% crude protein) or a diet with reduced level of protein (26%) but supplemented with a digestive/metabolic enhancer (AQUAGEST OMF, Nutriad) during 18 weeks. Different superscripts in the row indicate significant (P<0.05) difference between different dietary treatments. Values are means ± SD from three groups of fish (n=3) with 45 fish per group. FCR: food conversion ratio; PER: protein efficiency ratio (modified from Lin and Wu, 2014). CONTROL 28/7
LOPRO 26/7+AG
% change vs control
93.3±2.2
96.3±2.6
+3.2%
Survival (%)
Statistics
Initial wt (g)
177.3±1.8
174.7±2.1
-1.5%
Final wt (g)
469.6±13.2
482.0±12.1
+2.6%
Daily weight gain (g/d)
2.32±0.11
2.44±0.03
+5.2%
Feed intake (g/fish)
860.5±21.6
840.3±17.0
-2.4%
FCR
2.95±0.20b
2.74±0.04a
-7.1%
P<0.05
PER
1.22±0.08a
1.40±0.02b
+14.8%
P<0.05
Protein retention (%)
27.70±1.73
29.72±0.04
+7.3%
P<0.05
163±40a
267±29b
+63%
P<0.05
Hepatic G6PDH
14 | September 2017 - International Aquafeed