PSIII-26 True nutrient and amino acid digestibility of black soldier fly larvae fed different forms and concentrations of calcium using the precision-fed cecectomized rooster assay

Abstract

Abstract Black soldier fly larvae (BSFL) is an alternative protein source for animals, including dogs and cats. The larval diet may affect their nutrient composition and overall nutritional value. Calcium carbonate (CaCO3) and calcium chloride (CaCl2) are common Ca sources, but differ in solubility (CaCO3 is insoluble; CaCl2 is soluble), so their intestinal absorption may differ. In addition, the Ca form and concentration may decrease mineral utilization and nitrogen digestibility, thereby affecting feed conversion efficiency. Our objective was to determine the effects of different forms and concentrations of Ca on true nutrient and amino acid (AA) digestibility of BSFL intended for use in animal feeds using the precision-fed cecectomized rooster assay. All animal procedures were approved by the University of Illinois Institutional Animal Care and Use Committee prior to experimentation. 16 cecectomized roosters (4 roosters/substrate) were randomly assigned to test substrates. All contained 0.2% Ca in the commercial diet and additional Ca in these amounts and forms: BSFLA: 1.33% CaCl2; BSFLB: 1.0% CaCO3; BSFLC: 0.6% CaCO3; BSFLD: 0.5% CaCO3 + 0.7% CaCl2. After 24h of feed withdrawal, roosters were tube-fed 20g of test substrates. Following crop intubation, excreta was collected for 48h. Endogenous corrections for AA were made using 5 additional cecectomized roosters. All data were analyzed using SAS 9.4. True macronutrient and AA digestibilities were not different among substrates. Digestible indispensable amino acid score (DIAAS)-like values were calculated to determine protein quality according to AAFCO and NRC recommended allowances for dogs and cats. Although AA digestibilities did not differ among groups, those containing CaCO3 generally had higher DIAAS-like values than the diet containing CaCl2 alone (BSFLA). Threonine, methionine, and arginine were often the first-limiting AA. Our results suggest that Ca source fed to BSFL did not affect AA digestibility and protein quality, despite affecting total calcium content of the BSFL.