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Potential use of phototrophic algae as protein and/or lipid source in aqua-feeds

Published: October 21, 2016
By: Dr. Ingrid Lupatsch / AB Agri Ltd
In aquaculture, producers commonly rely on formulated feeds to ensure optimal growth, health and quality of the farmed animal. Fish meal and fish oil from wild fisheries have traditionally been major constituents of aqua-feeds as they are excellent raw materials from a nutritional point of view, but their supply is finite. Therefore feed ingredients other than fish meal are selected for their nutritive value, balance of amino acids, digestibility of proteins, lipids and quality of fatty acids, availability and cost. There is already a choice of protein substitutes on the market including animal by-products and plant proteins, however, very few resources contain the long chain omega three fatty acids EPA and DHA and thus algae biomass is being considered as one of the alternative ingredients of  the future.
 
The composition of micro and macroalgae vary considerably among species but also depending upon culture conditions. The average protein level in macro-algae is around 8 – 15% per dry matter, whereas the average lipid is only 1 or 3%. This compares to a protein content of 40 to 50% per dry matter for the micro-algae and lipid contents as high as 40%. Freshwater algae such as Chlorella and Spirulina seem to have a good potential as protein sources whereas marine microalgae such as Nannochloropsis, Tetraselsmis etc. are the fundamental source of the long-chain polyunsaturated fatty acids EPA and DHA. Without the DHA and EPA in aquafeed, the end product would also lack these long chain omega 3 fatty acids, an important nutritional element of fish and seafood for humans.
 
Nutritional studies evaluating the suitability of algae as feed supplement or fish meal substitute are currently few in number, due to the large amounts of algae biomass needed. Furthermore, each algae species possess their own characteristic nutritional properties (proteins, lipids, fatty acids, minerals, etc), not one formula fits all. In some cases the cellulosic cell wall poses a serious problem since it is not digestible for non-ruminants. A possible means of increasing the nutritional value of algal biomass would be to break down the cell wall fragments by mechanical treatment, or even by removal of most of the fibre, although such additional processing steps may add to the already high costs.
 
Thus, if a source of protein-rich or lipid-rich algal meal came onto the market at an affordable price, the aqua-feed industry would certainly consider using it. However, until supplies increase and costs decrease, algal biomass and biomass extracts will continue to occupy niche markets within the aqua-feed sector.
 
 
Presented at the European Aquaculture Society meeting 2016, Edinburgh, Scotland.
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Authors:
Ingrid Lupatsch
Swansea University
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Laurence Hutchinson
Freshwater Solutions- Ecological aquaculture
29 de agosto de 2019
Dear Dr. Ingrid Lupatsch, given that your data is pretty much a full description of the experimental evidence thus far,it may be an idea the break down the cell walls of these algae using ultrasonics as this kills the algal specie by actually breaking down the cell walls which thus kill the algal species targeted. I am aware that not all algal species have cell walls that will break down with ultrasound, by by varying the signal frequency and choosing the attack the algal species at a particular time in their growth cycle and before the walls thicken up too much one may be able to control the harvesting cycle to suit the particular algal sp. Given that fish only require a fifth of the amount of live feed to grow at for times the rate of farmed fish one can see that manufactured food is most inefficient and expensive way to produce farmed fish. Carnivorous species will and do grow amazingly well on live food and are under nourished on manufactured food. Yes, all fish are not the same and the way the way that they have continued to present susceptibility to farmed influences for the last 50 years must be worrying.. Thank you for your comments Dr. Ingrid Lupatsch.
Agwata Ototo
1 de febrero de 2017
Can we work on an isolation procedure of the algae and start its culture steps ?
Oyewo Oyeyemi
Olam Group
6 de noviembre de 2016
This is one of the areas that need serious development in aquaculture especially in Africa.
Eros Kaw
3 de noviembre de 2016
@ paul roberts, we use a specific bacteria to keep cyano bacteria away. and we grow chlorella to feed shrimps. we also grow daphnia and we feed the daphnia to trout and shrimp. but the key is chlorella. very high in protein. and the shrimps grow faster
Paul Roberts
28 de octubre de 2016
Algae are like any other agricultural crop; they get weeds growing among them. Discuss: How you control unwelcome algal invaders as some can toxic?
Akinwale Emmanuel
Aquapro Agro Industry
28 de octubre de 2016
How can we try this in Africa
Carlos Tay
28 de octubre de 2016
In my experience in Central America, with shrimp ant tilapia ponds, indicates that promoting micro algae in ponds has a very positive effect in the feed conversion rate (FCR). In average you can reduce your FCR in 0.2-0.4 enhancing de micro algae growth. Specially diatoms, Cyclothella sp. , Navicula sp, Chaetoceros sp, among others. Also this increase of algae will create a better dissolved oxygen condition during all day.
Biplab Banerjee
27 de octubre de 2016
Duck weed , Eichornia etc. all these types of aquatic floating weeds may be a good source of protein but fact remains they are good absorbers of heavy metals of various types too. Inclusion of these in aqua feed as ingredients needs verification. Dr.Biplab kumar Banerjee
Krishen Rana
26 de octubre de 2016

Market forces will dictate prices in relation to other sources not cost of production. Prices unlikely to come down. Limiting input resourses for such products will in all probality keep this as niche product.
The notion that you can make inroads into global use with such products in aquafeeds is a falacy, just as insect meal is which was in vouge some three decades ago. Academic cycles for grant funding seems to be the order of the day!

Louis Landesman
26 de octubre de 2016
Duckweed can provide a high protein, inexpensive source of protein in fish and livestock diets. Contact me on Linkedin for details: Louis Landesman, Ph.D
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