Background: The growing aquaculture industry has an increasing demand for novel protein sources for aqua-feed that are produced in a sustainable way.
Aim: To determine t he apparent digestibiltiy coefficients (ADCs) of four novel fungal feed ingredients in Rainbow trout, namely; Paecilomyces variotii (PEK), Aspergillus oryzae (AO), Rhizopus oligosporus (RO) and Rhizopus delemar (RD) .
Materials and Methods : All fungi were grown on various industrial side streams such as beet vinasse, thin stillage and whole stillage . The test diets were based on the multicellular fungi mentioned above and t itanium oxide was added as the inert marker . Diets were produced by extrusion technology. The diet ary treatments consisted of a control diet and test diets with 30:70 test ingredient: control. The experimental period lasted for 40 days . 20 fish were kept in each tank with 3 replicates per dietary treatment . One-way ANOVA was performed to compare the means of the groups with each other. p < 0.05 was considered significant.
Results: The DM digestibility of PEK was significantly higher than AO, RD and RO, all with similar digestibility . The crude protein ADC for PEK was 91.6% which is significantly higher than the other fungi sources. The ADC of AO and RO were 77.7% and 75.7%, respectively, which was significantly higher than that of RD which was 68%. The crude fat digestibility of the ingredients were 83%, 98.7%, 49.7% and 87.3% for AO, PEK, RD and RO, respectively . AO, PEK and RO have similar crude fat ADC compared to each other but RD has significantly lower crude fat ADC compared with the other ingredients tested.
Discussion: PEK seems to have high ADC for all macronutrients tested . A life-cycle analysis will further help in determining its suitability as an alternate, sustainable protein source for rainbow trout feed. Also, further growth performance trials are required to assess their potential as ingredients in aqua feed.
References:
Cho, E. Y. a. S., S.L. (1979). Apparent Digestibility Measurement in Foodstuff for Rainbow Trout. World Symposium on Fin Fish Nutrition and Fish Feed Technology , 239-247.
Langeland, M., Vidakovic, A., Vielma, J., Lindberg, J. E., Kiessling, A., & Lundh, T. (2016). Digestibility of microbial and mussel meal for Arctic charr (Salvelinus alpinus) and Eurasian perch (Perca fluviatilis ). Aquaculture Nutrition, 22(2), 485-495.
Acknowledgements:
Funding: Nordforsk and Formas Microbial ingredients: University of Borås and Eneferbio