Salmonids on Insect Protein – Impact on Performance and Health

In order to find out whether insects are suitable as a pure protein source and what potential problems or benefits can be expected, a 10-week feeding experiment was set up. In this experiment, the overall protein content were identical, while the protein content from soy and fishmeal was replaced with 25, 50, 75 and 100% insect meal. In order to evaluate the effect of the insect protein on the fish, fish size and weight were determined at the beginning and end of the experiment, and transcriptomic analyses of proximal intestine were performed. Finally, samples of the liver and intestine were examined histologically. The animal trial was conducted at the Fisheries Research Station of Baden-Württemberg (Langenargen, Germany) for a period of 69 days. The feeds were largely identical in their isocaloric and isonitrogenic composition. The feeds were based on soy and insect meal and optimized for rainbow trout of the age class used (6 months) and formulated with the objective of testing their effects on performance, health and faecal stability. Feed was manufactured by Skretting (Stavanger, Norway), who also provided the black soldier fly meal. Four different levels of insect protein, plus a control feed were produced, meaning that either 0, 25, 50, 75 or 100% of the protein content originating from soy meal was replaced by insect protein. Additionally, each feed was produced without and with 0.3% of the manure-stabilizing binder Guar Gum.