Chemical composition and amino acids of Locusta migratoria (Orthoptera Acrididae) fed wheat seedlings (Triticum aestivum) or rape leaves (Brassica napus)

Abstract

Locusts have high nutritional value and are considered alternative protein sources for humans and animals. Diet can strongly affect the nutritional composition of insects. In this study, the influences of diets – wheat (Triticum aestivum) seedlings and rape (Brassica napus) leaves – on the chemical composition and amino acids of the migratory locust (Locusta migratoria) were assessed. The crude protein, soluble carbohydrate and triglyceride were analyzed using the Bradford method, anthrone colorimetry, and glycerol kinase chromogenic method, respectively. Additionally, amino acids were determined using cation exchange chromatography. The study revealed that wheat seedlings had lower water content than rape leaves. Although the crude protein content was comparable, the soluble carbohydrates of wheat seedlings were approximately 2.5 times higher than those of rape leaves. The body weight (fresh weight and dry weight), crude protein and triglyceride of locusts significantly increased when fed wheat seedlings compared with when fed rape leaves, with values of 48.08%, 31.58%, 43.83% and 25.00%, respectively. The high water content of rape leaves resulted in the high water content of rape leaf-fed locusts. Plants also affect the amino acid composition of locusts. The eight amino acids (four essential amino acids and four non-essential amino acids) and the total amino acids of rape leaf-fed locusts were significantly enhanced compared with those of wheat seedlings. The essential amino acid index and biological value indicate that the protein quality of locusts fed rape leaves has been significantly improved. These results demonstrate that the nutritional composition of L. migratoria can be altered by manipulating the diet. Insects with controllable nutrients can be provided by insect farms and further studies will improve the development of insects as food or feed.