The total world production of fish meal and fish oil has been stagnant for many years, while aquaculture and livestock production has continuously increased, putting strong pressure on marine ingredients.
Traditionally, fish meal and fish oil have been the main ingredients in feeds for carnivorous fish species and to a lesser extent in feeds for marine shrimp. The main reason was that the nutritional requirements of most aquacultured species was not well known, and a fishmeal/oil based diet would produce good results of growth and survival. However, the total world production of fish meal and fish oil has been stagnant for many years, while aquaculture and livestock production has continuously increased, putting strong pressure on the marine ingredients. For many years, researchers have investigated the nutritional requirements of each aquacultured species, and the substitution of marine ingredients by other non marine proteins and fats.
We know now the amino acid requirements of most aquatic organisms, as well as the ideal protein/energy ratio in their feeds, so in theory, we could now produce feeds with 100 %
alternative (non marine) ingredients. However, in practice, when you substitute 100 % of the marine ingredients in the feed, even though you formulate to have the same amino acid profile and protein/energy ratio, you don’t get the same good results as if you used some marine ingredients in the feed. One reason is that marine ingredients contain elements and
compounds other that just amino acids (micronutrients, nucleotides, carnitine, phosphorus, just to mention a few). This can be solved by adding these nutrients in the feed, as additives.
But then, even if we have now a feed with the same characteristics as a fish meal feed in terms of nutrition, the lack of flavor/smell of marine ingredients in the feeds can have a negative effect on the feed performance. The feeding behavior of most marine fish and shrimp is usually modulated by the taste/smell/flavor of the feed. Some non marine ingredients have a taste that is not to the liking of many aquaculture fish/shrimp. Other raw materials have a neutral flavor, so the animals eat some feed, but not as much as they would with a feed made of marine ingredients.
In order to solve this palatability problem, there has been a lot of research to improve the feed palatability by the use of taste enhancers. Some of the taste enhancers used before are squid meal, poultry meal, krill meal, shrimp hydrolysates and fish hydrolysates. All of these palatants are more or less effective in enhancing the flavor/smell of the feed, and increasing feed intake.
In recent years, Rimfrost AS, a Norwegian biotechnology company, has developed a special krill hydrolysate, made from fresh krill caught in the pristine Antarctic waters. The fresh krill is
gently processed on board the fishing vessel directly after catch, using enzymatic hydrolysis (patented process). The resulting krill hydrolysate is naturally low in growth reducing
components such as fluoride and chitin while naturally rich in components that stimulates the feeding of fish by improved attractiveness and palatability (peptides, amino acids, growth
promotion factors and nucleotides). The result is a strong palatability that stimulates higher feed intake and better growth and survival.
In collaboration with Nofima (The Norwegian food research institute), Rimfrost has performed studies on Krill hydrolysate addition to Atlantic salmon feed. The results demonstrated a
significant increase in appetite, feed intake and growth of salmon smolts fed on diets with levels of 2.5 % or 5 % krill hydrolysate, compared to a standard control feed. During the first 6
weeks after transfer to sea water, salmon smolt fed on krill hydrolysate coated feed, doubled their weight, from 92 to 185 g mean weight (specific growth rate 1.6), compared to the control group with a final weight of 124 g (specific growth rate of 0.7), a specific growth rate more than double of the control feed.
The fish fed the krill hydrolysate were also more robust, suffering less scale losses, less wounds, and no hemorrhages. Later trials confirmed these results, showing that the application of krill hydrolysate on the feed coating performed better than in the feed core. Similar results were obtained in freshwater stage trials of smolts, indicating the benefit of the krill hydrolysate to enhance the feed intake and growth in all stages of culture.
In our first trials with shrimp, the use of krill hydrolysate allowed us to reduce the amount of fishmeal in the feeds by 30 %, without any decrease in growth, and better survival than the control group. New trials are ongoing, where the hypothesis is that we can replace higher levels of the fishmeal in the feeds without negatively affecting shrimp growth.
As confirmed from decades of research and Rimfrost’s own trials, the main beneficial effect of krill hydrolysates is the increased feed intake and corresponding increased growth rate. We
have also consistently observed better animal health and survival, suggesting benefits other than just the taste enhancing effect. Amino acids and peptides are for instance essential in shrimp and fish, and their fast uptake improves the robustness to stress events such as sea water transfer or low temperatures.
Krill hydrolysates in aquaculture feed hold a great potential to reduce the true costs of aquaculture production systems by improving several critical sustainability aspects.
