Insect meal in aquaculture feeds: with or without fat?

The search for novel raw materials to improve sustainability in aquaculture feed has led scientists and technologists to develop and produce new feeds using insect meal. The two most promising insect species, in terms of availability and nutritional profile, are the black soldier fly (Hermetia illucens) and the yellow mealworm (Tenebrio molitor).

Despite the progress, there are still many uncertainties that need to be addressed before making a specific decision. One of the most recurring questions is whether insect meal should be included with fat or without it. The choice of with or without fat will depend on the nutritional goals. For example, if the aim is to provide more energy in the diet and reduce the need for external oils, the fat from insects may be suitable as a substitute for vegetable or fish oils, but with limitations on the inclusion level due to this.

On the other hand, if the aim is to maximise the inclusion of insect meal in the diet, improve the fatty acid profile and optimise protein digestibility, defatted or partially defatted insect meal may be the best option.

For example, studies have shown that the black soldier fly (Hermetia illucens) contains 38% fat and the yellow mealworm (Tenebrio molitor) 19%. This means that if the strategy is to include the meal with fat, it should be noted that the lipid content of the diet could increase significantly, limiting the amount of insect meal that can be included without altering the nutritional balance, especially with regard to saturated fatty acids.

Conversely, if the aim is to maximise the inclusion of insect meal in the diet, improve the fatty acid profile, and optimise protein digestibility, defatted black soldier fly meal may be the better option.

Is the inclusion of insect meal in aquaculture diets viable? From a nutritional point of view, studies show that the inclusion of insect meal is viable. In the case of Atlantic salmon, this inclusion can reach up to 15% of yellow mealworm meal or 10% of black soldier fly meal without affecting growth, feed conversion, or the health indicators of the fish.

What other aspects should be considered when including insect meal with fat? Yellow mealworm meal seems to have a better profile of polyunsaturated fatty acids (omega-6), while black soldier fly is richer in saturated fatty acids. Regarding nutrient retention, although both are suitable, it is advisable to control the inclusion level to avoid a reduction in protein digestibility, especially at high fat levels.

Which of the two insect species is more suitable for feed production?

From a nutritional perspective, insect meals, whether with or without fat, are a choice for feed formulators based on ingredient availability and their strategies, as long as the inclusion levels are adequate and attention is paid to fat content to avoid unwanted effects on protein digestibility and overall feed quality.

In any case, all indications point to yellow mealworm meal offering the best balance between protein content, polyunsaturated fatty acid profile, and higher possible inclusion levels, making it more versatile and suitable for feeding fish species where a healthier lipid profile is desired. Additionally, the higher inclusion capacity helps reduce dependence on other protein sources, which is key to sustainability in aquaculture.