Biology subjects

Schou, T. M.

Publications and source records attributed to Schou, T. M..

3 recordsLinked to original sources

bioRxiv2025

Using gas exchange measurements to monitor growth, energy expenditure, and body composition of black soldier fly larvae (Hermetia illucens) on diets varying in protein-to-carbohydrate ratio

Optimizing black soldier fly larvae (BSFL) production requires a better understanding of how diet composition shapes growth, nutrient allocation, and metabolic efficiency. This study investigated whether respiratory measurements could serve as predictive, non-invasive tools for BSFL performance on diets differing in protein-to-carbohydrate (P:C) ratio. Larvae were reared for seven days on four experimental diets, with growth, survival, gas exchange (O2 consumption, CO2 production, respiratory exchange ratio (RER)), and body composition (crude protein and lipid contents) measured across seven replicates per treatment. O2 consumption correlated strongly with final larval biomass, while RER was closely associated with protein and lipid deposition. Larvae on low-protein, high-carbohydrate diets accumulated proportionally more lipid, whereas protein-rich diets increased crude protein content but required higher energetic investment. This demonstrates that lipid-rich larvae grew more efficient in energetic terms per unit accumulated biomass than protein-rich larvae. Across diets, gas exchange variables reliably reflected growth dynamics, metabolic activity, and nutrient assimilation. Integrating respirometry into rearing systems could enable real-time monitoring of insect biomass yield and nutrient composition.

physiology↗

bioRxiv2025

Consequences of dietary amino acid imbalance on growth and gas exchange in black soldier fly (Hermetia illucens) larvae

Black soldier fly larvae (Hermetia illucens (L.); BSFL) production relies on efficient nutrient conversion into protein-rich biomass to ensure sustainability and economic viability. While the effects of dietary protein content and macronutrient ratios are well described, the metabolic costs of providing an imbalanced essential amino acid (EAA) supply in dietary proteins remain poorly understood. We examined how dietary EAA imbalance affects growth, metabolism, and energy allocation in BSFL. Larvae were reared on a reference diet (chicken feed) and three isonitrogenous, semi-synthetic diets: one balanced diet matching the EAA profile of the reference, and two unbalanced diets selectively deficient in either leucine, phenylalanine, and threonine or isoleucine, lysine, and tryptophan. Using open flow respirometry, daily growth monitoring, and biochemical analysis, we quantified gas exchange, body composition, and the energetic costs of biomass and protein deposition. EAA imbalance delayed development, reduced growth and protein content, and promoted lipid accumulation, while O2 consumption and CO2 production were reduced and respiratory exchange ratios exceeded 1.0, indicating elevated lipogenesis. Metabolic costs per unit protein deposited were higher on EAA-deficient diets (up to 3.63 kJ per kJ protein), reflecting inefficient amino acid utilisation. In contrast, the balanced diet supported more efficient protein deposition at a lower energetic cost (2.73 kJ per kJ protein). Our findings demonstrate that suboptimal dietary EAA profiles reduce metabolic efficiency in BSFL. Quantifying the physiological costs of amino acid imbalance provides benchmarks to guide feed formulations in insect production systems to minimise input costs and maximise the nutritional quality and quantity of larval output.

physiology↗

bioRxiv2024

Controlled and polygynous mating in the black soldier fly: advancing breeding programs through quantitative genetic designs

In animal breeding programs, utilizing quantitative genetic designs such as the full-/half-sibling design is fundamental. A full-/half-sibling design demands that mating can be controlled, and individuals can be tracked, enabling construction of a pedigree. In nature, black soldier fly (Hermetia illucens (L.)) males are reported to gather in lekking groups to engage in competitive displays and courtship rituals before mating, and this lekking behavior is described as crucial for mating in this species. We show that a randomly chosen male and a randomly chosen virgin female can readily mate under LED lights in a small container at 28 {degrees}C and 70% RH, demonstrating the ability to mate selected pairs. For males given access to four females, all mated and the time until first mating was considerably shorter than for males given only one female, where 80% of the males mated. Furthermore, when adding four virgin females to a single male, males successfully mated all four females in 52% of cases within our four-hour trial, with 96% of males mating at least twice. Number of matings observed for a male correlated with the number of females from the container that laid an egg clutch, and almost all egg clutches produced offspring. Observed mating thus lead to fertilization, and consecutive matings were with new females resulting in full- and half-sibling offspring. Males with four females that mated a second female did so at a median time of less than three minutes upon ending previous mating, showing that polygynous mating occurred rapidly in this setup. Our findings pave the way for moving H. illucens breeding programs beyond mass selection towards advanced selective breeding designs where controlled mating is typically required. Such designs enable selection for multiple traits simultaneously while controlling inbreeding and can drastically increase rates of selection responses compared to mass selection.

animal behavior and cognition↗