Nutritive value of cereal grains, protein meals and by-products for yellow mealworms

Abstract

Abstract Nutritive value of raw materials is needed to formulate diets that fulfil the requirements of the yellow mealworms. The objective of this study was to determine the nutritional value of six raw materials commonly used in yellow mealworm feeding (barley grain, corn grain, hominy feed, wheat bran, corn gluten feed and soybean meal) and to propose prediction equations for the nutritive value of raw materials from their chemical composition. From Monday to Friday 5 g of raw material and 20 g of gel (source of water and micronutrients) were daily supplied. After two days of fasting, frass was collected. This procedure was repeated for 6 weeks. During this period, the initial and final weight of the larvae, the consumption of the raw material offered, and the production of faeces were controlled. Raw materials and faeces were analysed for dry matter (DM), ashes, crude protein (CP), ether extract, acid detergent fibre (ADF) and gross energy (GE), from which their coefficients of digestibility were determined. The digestible energy (DE) content of the raw materials was 13.8, 14.2, 11.6, 8.7, 6.9, 11.3 MJ DE/kg DM and the digestible protein (DP) was 61, 52, 48, 74, 70 and 242 g DP/kg DM for the barley grain, corn grain, hominy feed, wheat bran, corn gluten feed and soybean meal, respectively. DE content of raw materials was closely correlated with their content on ashes, starch and ADF (−0.83, +0.69 and −0.65, respectively; ), while DP content was mainly correlated with their content on CP, starch and ether extract (+0.95, +0.60 and −0.69, respectively; ). It can be concluded that mealworms have a good ability to utilize cereal starch, wheat bran diets should be complemented with digestible carbohydrates and protein sources, and soybean meal may be a good source of vegetable protein for mealworms.