The effect of black soldier fly (Hermetia illucens) larvae fractions in diets for Atlantic salmon (Salmo salar) on extruder parameters, pellet quality, growth performance and nutrient utilization

Abstract

This study focused on the effects of dietary inclusion of black soldier fly larvae (Hermetia illucens) fractions on extruder parameters, pellet quality, growth performance and nutrient digestibility and utilization in Atlantic salmon (Salmo salar). The different types of diets used were full-fat, defatted, dechitinized, BSFL oil and exoskeleton diets. For the diets containing BSFL meals, 15% of the dietary protein was replaced with insect protein. BSFL inclusion of full-fat and dechitinized BSFL in the diet led to low energy inputs during extrusion due to high lipid content in the insect, which resulted in lower durability, hardness, expansion and water stability of the pellets. In the fish experiment, 900 Atlantic salmon of 28 g initial weight were distributed in 18 tanks and fed with one of the diets for 62 days. The final bodyweight, body weight gain and specific growth rate did not differ in fish fed defatted, BSFL oil and exoskeleton diets compared to the control diet, whereas, they were higher in full-fat and dechitinized diets. Feed intake was similar among different BSFL diets and control diet, except higher for fish fed full-fat BSFL diet than other diets. However, feed conversion ratio was similar among fish fed BSFL diets and control diet. Apparent digestibility coefficient of dry matter, ash, starch and lipid were not affected by the dietary treatments whereas protein digestibility was lower in fish fed with defatted, dechitinized and exoskeleton diets compared to control diet. The apparent protein retention was not affected by dietary treatment, whereas the fish fed defatted BSFL obtained higher protein efficiency ratio compared to the control fed fish. In contrast, all BSFL diets had lower lipid efficiency ratio and apparent lipid retention than control diet, whereas lipid retention of fish fed dechitinized and control diet were similar. Phosphorus retention were similar among the diets except for defatted BSFL diet, which had higher retention of phosphorus compared to the control diet. Overall, growth performance of BSFL diets in Atlantic salmon was either better or similar to control diets whereas, lipid efficiency and lipid retention was reduced, except for dechitinized diet which showed similar lipid retention to control diet. Protein digestibility, on the other hand, was reduced by defatted, dechitinized and exoskeleton diets whereas, phosphorus retention was improved by defatted diet.