Digestibility of defatted insect meals for rainbow trout aquafeeds

Abstract

The apparent digestibility coefficients (ADCs) of the dry matter (DM), crude protein (CP), ether extract (EE), gross energy (GE), amino acids (AA), and the main fatty acids (FA) of four defatted insect meals in rainbow trout (Oncorhynchus mykiss) have been assessed. The tested meals were obtained from two yellow mealworms (Tenebrio molitor – TM1 and TM2), one black soldier fly (Hermetia illucens – HI) and one lesser mealworm (Alphitobius diaperinus – AD). The experimental diets were prepared by means of the substitution method, with each test ingredient included in the diet at 30% on an as fed basis and using Celite® as an inert digestibility marker. Eighty rainbow trout (140±5.6 g) were stocked in tanks connected to an open water system. Faeces were collected over four consecutive weeks using an automatic collection device after feeding the fish. The ADCs of the DM, CP and GE of the insect meals differed significantly, with the AD meal displaying the lowest values. The ADC of the EE in the different meals did not vary. As far as AA digestibility is concerned, the ADC of methionine changed according to the following pattern TM2=HI>TM1>AD, whereas the ADCs of cysteine and tyrosine were significantly lower in the AD meal than in the other meals. The ADCs of the main FAs (C12:0, C14:0, C16:0, C18:1 c9, C18:2 n-6 and C18:3 n-3) were higher than 85% and did not differ significantly in the insect meals. Overall, the tested insect meals resulted to be highly digestible and the differences among them depended on both the insect species and the specific production techniques of the meals. These results provide useful data that may be considered to properly formulate compound diets for rainbow trout using innovative protein sources.

Effects of dietary substitution of fishmeal by black soldier fly (Hermetia illucens) meal on growth performance, whole-body chemical composition, and fatty acid profile of Pontastacus leptodactylus juveniles

“…The lower growth and feed efficiency was not attributed to a lower feed acceptance, as the HM-fed crayfish exhibited a similar feed intake with the control group but may be due to a lower digestibility and/or to lower dietary essential amino acids. The digestibility of HM in fish is considered to be high and close to that of fishmeal ( Arango et al, 2004 ; Bosch et al, 2016 ; Gasco et al, 2022 ), but its high chitin content may also lower its nutrient digestibility ( Kroeckel et al, 2012 ; Dumas et al, 2018 ). Regarding amino acids, HM is known as a good source of lysine, but it is limited in methionine ( Makkar et al, 2014 ).…”

Factors affecting the decision-making process of using insect-based products in animal feed formulations

“…There are internationally recognised protocols to assess the digestibility of an ingredient in fish (Bureau et al, 1999), poultry (Ravindran et al, 1999(Ravindran et al, , 2017 and pigs (Zhang and Adeola, 2017). Even if several studies using insect-based products also assessed diet digestibility, data regarding the ADC of the single insect-based products are quite limited (fish: Basto et al, 2020;Fontes et al, 2019;Gasco et al, 2022;Mo et al, 2019;poultry: De Marco et al, 2015;Mwaniki et al, 2020;Schiavone et al, 2017;pigs: Tan et al, 2020). In vitro protocols have also been assessed (Kovitvadhi et al, 2019;Rodríguez-Rodríguez et al, 2022).…”

Insect meals in a circular economy and applications in monogastric diets

“… FF, full-fat insect meals; DF, defatted insect meals. a ( Weththasinghe et al, 2021 ; Leeper et al, 2022 ) b ( Heide et al, 2021 ; Weththasinghe et al, 2021 ; Gasco et al, 2022 ; Heuel et al, 2022 ; Silva et al, 2022 ) c ( Benzertiha et al, 2020 ) d ( Heide et al, 2021 ; Gasco et al, 2022 ) e ( Makkar et al, 2014 ; Hall et al, 2018 ) …”

“… b ( Heide et al, 2021 ; Weththasinghe et al, 2021 ; Gasco et al, 2022 ; Heuel et al, 2022 ; Silva et al, 2022 ) …”