Sago palm weevil larvae: larval ontogeny and nutritional value assessed from enzymatic activity and in vitro digestibility

Abstract Sago palm weevil larvae (SPWL, Rhynchophorus vulneratus ) have potential for use as food and feed. This study aimed to investigate their development, digestive enzyme activity, nutrient values, and digestible protein using an in vitro digestibility technique. Bioassays for SPWL at 21, 28, 35, 42, 49, and 56 days after hatching (DAH) were conducted in a completely randomized design (CRD). Analysis of variance (ANOVA) was performed, and means were compared at using Bonferroni (Dunn) t-tests and orthogonal polynomial contrasts. Trypsin activity significantly increased at 35 DAH ( , quadratic effect ), with peak chymotrypsin activity at 28 DAH ( ). Lipase activity showed both linear and quadratic increases ( ), and cellulase activity also increased significantly ( , linear and quadratic terms ). Meanwhile, the A:T ratio increased significantly ( , quadratic effect ) with age-related rises in these digestive enzyme activities. The highest crude protein content in SPWL was observed at 42 DAH ( ), with peak carbohydrate at 28 DAH ( ). Phenylalanine and histidine levels increased linearly ( ), while lysine and total essential amino acids peaked at 42 DAH ( , linear and quadratic terms ). Levels of linoleic acid, total polyunsaturated fatty acids, and the n-6:n-3 ratio peaked at 49 DAH ( ). In vitro protein digestibility assays were performed using enzymes extracted from quails, broilers, Thai native chickens, and ducks. Significant increases in digestibility were attributed to SPWL protein content and age, particularly beyond 42 DAH ( , linear and quadratic terms ), except with duck enzymes. In conclusion, these findings suggest that SPWL cultivation, particularly between 42 and 56 DAH, provides a potential alternative protein source with substantial nutritional benefits for poultry feed. The promise of SPWL to contribute to more sustainable and efficient poultry feeding practices is evident, and further in vivo studies are warranted to validate these results.