Much research has been directed towards the optimisation of the mass rearing of the yellow mealworm, Tenebrio molitor, in terms of diet and rearing conditions. However, an issue that has not been thoroughly investigated to date is the strain effect on the larval growth and performance of T. molitor. To close this gap, the plasticity in growth and development, as well as the feed conversion efficiency and the nutritional composition of larvae of seven T. molitor strains of different geographic origins (Greece, Italy, Germany, Turkey, Spain and USA) were comparatively evaluated in the present study. Based on the results, there were considerable differences in the performance of the strains tested. Larval weight at harvest was the highest for a strain originated from Germany; however, the higher final body mass was at the cost of longer development time and higher feed intake, the latter having a negative impact in the overall performance and productivity of the strain. No significant differences were detected in the larval nitrogen and lipid content among the strains tested. In overall, the Italian strain II had the best growth performance in terms of survival, larval biomass production, development time and feed utilisation. The present study aims to highlight the need for selection of strains with enhanced performance and production traits for mass-production, which will boost the overall productivity of insect farming systems.
Lately, additional attention is being placed on edible insects, since they constitute an excellent, cost-efficient source of proteins with a low ecological footprint. Tenebrio molitor was the first insect that was considered edible by EFSA in 2021. This species can replace conventional protein sources and thus, it has the potential to be used in many different food products. In the present study, a food by-product that is commonly produced (i.e., albedo orange peel waste) was used as a feed additive for T. molitor larvae, in an effort to further improve the circular economy and enhance the nutritional value of the insects. To this end, bran, which is commonly used as feed for T. molitor larvae, was fortified with the albedo orange peel waste (up to 25% w/w). Larval performance, in terms of larval survival and growth, as well as the larval nutritional value, i.e., the content of protein, fat, carbohydrates, ash, carotenoids, vitamins A and C, and polyphenols, was evaluated. Based on the results, the increase in the percentage of orange peel albedos in T. molitor feed resulted in a subsequent increase in the content of larvae in carotenoids and vitamin A up to 198%, in vitamin C up to 46%, and an increase in the protein and ash content up to 32% and 26.5%, respectively. Therefore, the use of albedo orange peel waste for feeding of T. molitor larvae is highly recommended, since it results in larvae with enhanced nutritional value and at the same time, the utilization of this feeding substrate further lowers the cost of insect farming.
Mass rearing of Tenebrio molitor L. (Coleoptera: Tenebrionidae) is currently at its infancy, looking for new strategies in order to ameliorate its capabilities. That being the case, several efforts have been made towards optimisation of rearing methods of the larval stages, while more recent research is also directed towards optimisation of the reproductive output of T. molitor adults. Yet, there are very few published data concerning the strain effect on the adults’ performance. Thus, the aim of the present study was to comparatively evaluate fitness-related traits, i.e. adult survival, egg production and hatching rate, of six T. molitor strains from five countries (Greece, Italy, Germany, Turkey and Spain). Based on the results, considerable differences were detected in the fitness-related traits of the strains tested. The highest cumulative egg numbers were recorded for the Spanish, the Italian I and the Greek strain, in contrast to the German one which had the lowest cumulative number of eggs. Hatching rate and survival was high for all strains tested, with the exception of the German strain. In general, the reproductive output for the Greek strain was the highest, both in terms of egg production and hatching rate. The results of our study aim to emphasise on the need for proper strain selection taking into consideration, apart from larval growth and performance, the progeny production capacity of adults, in order to increase the efficiency of T. molitor production.
Edible insect production relies, among others, on the use of high-quality strains with good productivity characteristics. However, studies on the evaluation of the growth performance of different insect strains are limited. In this framework, the objective of the present study was to evaluate the growth and development under dry conditions of larvae of six Tenebrio molitor strains of different geographical origins, i.e. Greece, Italy, Turkey, Spain and USA, in terms of larval survival and development, as well as feed utilisation efficiency. In light of our results, we report the variable growth performance of different T. molitor strains in the absence of a moisture source. Although no significant differences were shown among the strains tested with regard to the final larval weights and survival rates, there were significant differences in the development time and the growth rate, which may affect the overall efficiency of T. molitor larvae production. Our study aims to highlight the significance of strain for the growth performance and consequently the productivity of T. molitor.
The fast-growing sector of insects for food and feed stimulates researchers and the industry to explore uncharted territories, such as insect breeding, to improve economically important insect fitness traits. The yellow mealworm, Tenebrio molitor L., is one of the most thoroughly studied insect species as food and feed. However, data on mating compatibility and the effect of cross-breeding between different strains on the performance and fitness of the hybrids are scarce. In the present study, we comparatively evaluated the mating compatibility between two T. molitor inbred strains (Greek and Italian) and their outbred strains, i.e., Italian (♀)-Greek (♂) and Greek (♀)-Italian (♂), as well as the performance of their hybrid offspring. Based on the results, there is good mating compatibility among adults of the strains tested. Offspring performance, quantified as larval survival and final larval weight, followed a similar pattern among the crossings examined. Even though differences were insignificant, the outbreeding of females of the Italian strain resulted in a higher cumulative number of eggs and hatching rate and higher offspring weight. The present study sheds light on the mating compatibility of different T. molitor strains and their hybrids' economically important life table characteristics to take the mass production of insects one step further.
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