Major development is underway within the field of nutrition and feed regarding broadening the spectrum of raw materials for feed. This initiative is important in order to make farmed fish a net producer of marine protein, and to have a buffer with access to raw materials of fluctuating prices and quality.
The research initiative to broaden the choice of raw materials for production of salmon feed is also reflected in commercial production, which is gradually becoming less reliant on fishmeal and fish oils.
The charting of essential components in the marine raw material of significance to the production result of the fish, and the optimising of these in commercial feed, can open opportunities for increased use of alternative and cheaper protein raw materials in feed.
However, this requires knowledge about production of balanced feed with respect to amino acids, fatty acids and minerals, as well as knowledge about interactions with intake and conversion of nutrients and control of anti nutritional components in marine and plant ingredients.
Nofima has specialised in raw materials and process competence of significance to the quality particularly of marine feed raw materials. However, it also has considerable competence in the use of a host of different feed raw materials of vegetable and plant origin, including different types of soya bean, corn, wheat and pea meal products documented in feeding trials involving salmon and cod.
The quality of marine feed oils is another research topic that has also been documented with biological testing of salmon.
Fishmeal and fish oil
Fishmeal and fish oil were previously the dominant ingredients in salmon feed. Price wise fishmeal was a relatively cheap source of protein, relatively easy to source, of predictable quality and was a well balanced source of protein. This was important as protein accounted for 45 percent of the ingredient cost in the feed. Marine protein and fat remain important ingredients in fish feed. On a global basis, around 60 to 70 percent of all fishmeal produced is used for fish feed and between 80 and 90 percent of all fish oil is used for the same purpose.
Fishmeal or fish oil will remain an important ingredient in fish feed as farmed fish require at least one percent of marine fish oil in their feed. In a fishmeal-based diet, the entire proportion of oil may come from vegetable sources without reducing the fish's performance or health. However, it is important to stress that the fatty acid profile in the fish will reflect the feed.
By-products from farmed fish
Trimmings from the fish processing industry create a significant amount of waste or by-products. The fillet yield varies from less than 30 percent in the production of surimi to 60 percent in production of salmon fillet. As a result, the by-products from aquaculture as well as fisheries are an important source of protein. These by-products can be processed fresh, such is the case with the products for human consumption, and as such have a high nutritional quality that can be of special value when used in tandem with plant protein and animal by-product meal.
If several species can be farmed in relatively balanced quantities, the slaughter waste from one species can be a valuable source of protein and fat for another species. The aquaculture industry has on average 50 percent waste. If much of this can be used for fish meal, the amount of waste can be reduced to 10 percent of the production volume. This will constitute two-thirds of the amount of fishmeal that is used for the production of a carnivorous fish such as salmon. Consequently, aquaculture will soon be in a position where it is self sufficient with proteins, which will have a dramatic effect on the industry's sustainability.
In the EU, the use of protein from animal by-products has been prohibited since 2000 because of an outbreak of mad cow disease. Blood meal from non-ruminating animals was permitted again in the EU in 2003 and in Norway in 2007.
Raw materials from the plant kingdom
Since fishmeal and fish oils are limited resources and are expensive compared to many other raw materials, sustainability and financial considerations provide an incentive to use other sources. However, some plant raw materials contain antinutritional factors, which can influence the fish's health and utilisation of nutrients. This is particularly a problem for carnivorous fish, which nature has not adapted to a vegetarian diet. It is therefore necessary to acquire knowledge about antinutritional factors from plant raw materials before such raw materials can be fully used in a commercial context.
It is also important to know about the amount of utilisable nutrients in each feedstuff. The amino acid composition in plant protein sources is different than in fish meal, and in combinations of several feedstuffs, and supplements of some amino acids may be necessary to cover the fish's needs. The most relevant vegetable protein sources are various soya bean products, rape seed oil, wheat gluten and corn gluten.
There are several possible vegetable fat sources for fish feed, including soya bean oil, rape seed oil, palm oil and sunflower oil. Oil-rich raw materials from the plant kingdom may be used to a high degree as fat sources for salmon feed as long as the minimum requirements for essential fatty acids of one to two percent of the diet are fulfilled. Even though plant raw materials do not contain long-chain omega-3 fatty acids, Nofima has proven that salmonids to some extent can produce such fatty acids based on fatty acids supplied from vegetable oils. However, this production is not large enough to maintain a fish oil profile in the fish muscle.
Further description
