# Accessing the impact of harvest weights of Tenebrio molitor on amino acid digestibility and metabolizable energy in cecectomized laying hens

## TL;DR

This study examines how the harvest weight of Tenebrio molitor larvae and pupae affects amino acid digestibility and energy in laying hens.

## Contribution

The study introduces findings on how pupae of Tenebrio molitor offer higher amino acid digestibility and energy compared to larvae.

## Key findings

- Amino acid digestibility and metabolizable energy were higher in pupae compared to larvae.
- Partially defatted TM larvae of different weights showed no differences in amino acid digestibility or energy.
- Pupae could reduce nitrogenous emissions in egg production if their production emissions remain low.

## Abstract

The effects of harvest weights on composition, amino acid (AA) digestibility and metabolizable energy (MEN) of Tenebrio molitor (TM) were investigated using cecectomized laying hens. The partially defatted and dried TM variants comprised median individual frass‐free harvest weights of 60, 80, 100, and 120 mg of larvae, and a pupae weight of 125 mg. Diets containing the five TM variants and a basal diet were fed to six cecectomized laying hens over six experimental periods in a 6 × 6 Latin square design.

The AA concentrations relative to crude protein were similar among the TM larvae variants. Crude protein and crude fat contents did not differ between the larvae variants. Pupae had a lower crude protein and a higher crude fat concentration compared to the larvae variants. The AA concentrations in the fat‐free dry matter of TM were low for all harvest weights. Larvae variants did not differ in AA digestibility, whereas pupae showed the highest values. Compared with pupae, larvae had a lower digestibility (P ≤ 0.050) for all AA except Arg and Thr in L60; Arg, Asx, Glx, Lys, and Thr in L100, and all AA except Arg, Asx, Glx, Leu, Phe, Pro, and Thr in L120. The MEN did not differ among larvae variants but was higher for the pupae (P ≤ 0.050).

The present study did not indicate that partially defatted TM larvae of different harvest weights influenced AA digestibility and MEN, whereas AA digestibility and MEN of pupae was higher. Feeding partially defatted TM pupae instead of larvae could reduce nitrogenous emissions during egg production, provided that emissions from pupae production remain low. Therefore, optimizing the defatting process for TM pupae may help mitigate challenges associated with the higher fat content, potentially enabling the realization of the benefits from its higher AA digestibility in feed applications. © 2025 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.