Replacing Fish Meal and Fish Oil in Aquaculture

Some aquaculture species, such as salmonids and crustaceans, are major consumers of fish meal and fish oil. Such feeds come from industrial fisheries and fish processing. What could be done to compensate if fish meal and fish oil are ever lacking? Increasing the share of plant-based ingredients in fish feed works as a privileged alternative. However, plants do not have the same nutritional properties as fish byproducts, so what are the guidelines to follow for finding substitutes?
 

Several factors must be considered in the event that the share of plants in fish feed is increased. What are these factors?

The rebalancing of plant ingredients’ nutritional inputs in fish meal

Fish meal is undoubtedly a main source of essential amino acids for fish. Fish meal is valuable in its rich content of highly digestible and well-balanced proteins. Choosing plant-based ingredients as an alternative to marine raw materials allows the fish’s high requirement  of balanced and easily digestible proteins is met. Meal or protein concentrates from soybeans, canola, peas etc.can be used for this purpose. A good mixture of plant ingredients can also help balance the supply of essential amino acids. Special attention also ought to be paid to anti-nutritional factors; some plant raw materials contain these compounds which can prevent the feed from being well digested. These are likely to resist the feed processing and therefore remain in the finished feed.

Elements such as phytoestrogens (found in lupine, soybean or alfalfa for example) can thus disturb the hormonal cycle of certain breeding species. Another example of this kind of element is gossypol. Found in cottonseed cake, it can decrease the performance as well as the level of ingestion of  some species. Another risk worth mentioning associated with these factors is the mycotoxin content of plant raw materials.

Fish meal contains a significant amount of minerals that are well digested by various aquatic species. The possibility of readjusting phosphorus, calcium and other minerals levels should therefore be considered as a potential alternative for instance at the formulation stage.
 

A few equivalents to fish oil

In addition to being highly sought after by consumers, long-chain polyunsaturated fatty acids are essential nutrients for the growth of aquatic animals. For this reason, the fatty acid profile of farmed fish and shrimp are heavily influenced by the lipid composition of their ingested feed. Some species, including freshwater ones, have the ability to synthesize polyunsaturated fatty acids. Yet marine fish, such as seabass or seabream, are completely devoid of this ability. It is therefore through their feed that these essential fatty acids must be provided to them.
However, raw materials that can provide such nutrients without being derived from fish processing scarcely exist. Microalgae, insect meal and GM plants are among some possible substitutes. While the two first options have only barely been explored, the use of GMOs has proven relatively successful from a zootechnical  point of view. However, this option still has a long way to go before it can gain widespread acceptance, especially within the European Union.
 

Whatever your feed issue, experts from the TECHNA Group are at your service, thanks to our thorough knowledge, experience and accuracy in meeting farm animals’ nutritional needs.   We assist feed manufacturers in finding alternatives to fish by-products for the benefit of plants. For more information, please don’t hesitate to contact our experts at the TECHNA Group.