Experimental feeding studies with crickets and locusts on the use of feed mixtures composed of storable feed materials commonly used in livestock production.

Abstract

Insects such as the Mediterranean field cricket, Gryllus bimaculatus and the Desert locust, Schistocerca gregaria, are emerging as potential sources of human food and feed for livestock. High nutritive value and efficient feed conversion make them attractive for commercial production as novel livestock, but these properties strongly vary with the insects´ diet. Current mass-rearing protocols are based on fresh, non-storable feed materials. This requires constant supply and makes the systems sensitive to fluctuations regarding nutritional quality and safety. Hence there is a need to find storable, readily available feeds. Therefore, experimental diets were composed from the five different feed materials, corn meal; soya extracts; dried cowpea leave; corn stover; dried carrot; and a vitamin supplement. The diets were formulated such as to vary in macro-nutrient and vitamin content. Effects of these diets on consumption, biomass gain, feed conversion and nutritional composition of the insects were assessed. Crickets were fed a combination of corn meal and cowpea leave (“Starch”) and a combination of soya extract and corn stover (“Protein/fiber”). Locusts were fed “Starch” and “Protein/fiber” and variations of these, supplemented with vitamins and carrot (“Protein/fiber/carrot” and “Starch/carrot”). Additionally, a combination of cowpea leaves and soya extract, supplemented with vitamins and carrot (“Protein/carrot”), was tested on locusts. Crickets grew and gained biomass relatively well when fed “Starch” but struggled with digestion of the high-fiber diet “Protein/fiber”. Locusts fed “Starch” and “Protein/fiber” failed to gain biomass or performed poorly. When supplementing these diets with vitamins and carrot, locusts on “Starch/carrot” failed to grow while locusts fed “Protein/fiber/carrot” could gain biomass and showed excellent feed conversion. Accordingly, vitamin supplementation of this diet had a positive impact. Locusts fed “Protein/carrot” showed the best results regarding feeding efficiency and production figures. All tested feed materials were accepted by the insects. Therefore, these feed materials may replace fresh feed materials and may thus improve efficiency and safety of insect production systems. Indeed, certain diet formulations revealed nutritional limitations. They might serve as model diets to derive nutritional requirements of insects e.g. for protein, amino acids or vitamins.