Changes in aquaculture: New diets, new testing

The aquaculture sector is growing. But to do this sustainably, the feed ingredients have to change, and with that, the analytical methods. How to deal with new protein sources for farmed fish is, therefore, one of the key research topics worldwide.

Fish nutrition and aquaculture was one of the key topics at the recently held International Feed Conference (Feed 2018): Present and Future Challenges, which took place in Bergen, Norway. A number of key experts in the field of animal nutrition, ingredient testing and aquaculture came together at the end of October to discuss the latest issues that today’s animal feed sector and fish farming is facing. Here we explain some of the highlights of the event.

The aquaculture sector is a fast growing food-producing sector, but still relatively untapped, considering that the world is covered for 70% by oceans. Around 45% of the seafood consumed is farmed, the rest comes from wild catch. Although the percentage of farmed fish will probably soon be higher than the wild catch percentage, it still has a lot of room for growth. At the same time, with the world population increasing in the coming decades and the associated increased demand for animal protein, the need for protein sources such as fish (that can be eaten by all cultures and is often considered a healthy animal protein) is huge. Knowing that only 6.5% of all the total protein consumed on a global level comes from fish and other aquaculture species, it is obvious that aquaculture is one part of the solution to feed the hungry mouths of the growing world population.

In species that have farmed for a long time already, such as salmon, we have seen a great improvement of diet formulation and the feed conversion ratios (FCR) over the years. Feed represents a considerable part in the total costs for a fish farm, so optimising the amount of feed needed is key. In Atlantic salmon for example, the FCR has improved from over 3 in 1975, to 1.5 in 1990 to around 1.3 today. This has been the result of selective breeding, nutrient requirement studies and improved feed technology. This makes the Atlantic salmon a champion in turning feed into animal protein. Feed conversion ratios of other farmed aquaculture species are somewhat higher (worse): Seabass (2.0), common carp (1.5-3.5), pangasius (1.7-3.0) and Vannamei shrimp (1.4-1.8). But not only the FCR has changed, also the way a fish diet is built up has changed considerably. Vegetable ingredients (for example soy and wheat gluten) are replacing marine ingredients (fish meal and fish oil). In 1990, a typical salmon diet did not have any plant based materials in it. Since 2000, that started to change, when plant oil (often rapeseed oil) were added, and partly replaced the fish oil inclusion. A typical salmon diet of today has more plant based oil and plant based protein included than marine ingredients. Experts even say that 100% replacement of marine ingredients by plant based ingredients is possible from a nutritional standpoint.

By Emmy Koeleman

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