Amritha Johny defends her thesis December 4, 2020

November 23, 2020 Off By Ingunn Samdal
Amritha Johny

Amritha defends her thesis “Plant-based aquafeeds: Carry-over potential of mycotoxins and phytoestrogens from feed to fish and implications for fish health and food safety” on December 4th at the Norwegian University of Life Sciences (NMBU). She has performed her studies as part of the Havbruk2-project “SafeFish” in the Research group for Chemistry and Toxinology at the Norwegian Veterinary Institute.

Feed for farmed fish contains nowadays mostly plant ingredients because there are not enough marine raw materials to cover the growing demand. Plants commonly used in fish feed are wheat and legumes such as soybean and pea. The significant changes in the feed can have consequences for the fish and for the consumers of fish-based food. The main concerns are connected to the presence of plant-borne contaminants including endogenous anti-nutritional factors (ANF) such as natural toxins and phytoestrogens.

In her work, Amritha has evaluated the impact of “green” aquafeeds containing wheat gluten, soybean protein concentrate or pea protein concentrate in dietary exposed zebrafish and on-growing salmon by studying ANF transmissibility and elimination in the fish as well as changes in different organ transcriptomes. The results showed that under the chosen experimental conditions, using commercially available Norwegian feed ingredients, the inclusion of plant-based ingredients into aquafeeds is not of concern for consumers of salmon products regarding potential health risks from the carry-over of mycotoxins and phytoestrogens. While mycotoxins were present only in trace amounts, as measured by a newly developed and validated multi-analyte liquid chromatography mass spectrometry method, phytoestrogens were effectively metabolised by glucuronidation reactions in the fish. The two novel in vitro liver metabolism assays for salmon developed in this study are suitable tools to investigate the biotransformation pathways of a wide range of compounds in future applications. Wheat gluten- and soybean-containing had, however, at higher inclusion levels a significant effect on the gene expression patterns in the muscle tissue, liver and intestine of zebrafish and salmon. The results indicated a negative impact of the diets on fish health, especially with regard to enteropathological inflammation.

Amritha was mentored by Christiane Kruse Fæste (NVI), Tone-Kari Knutsdatter Østbye (Nofima), Jorge M.O. Fernandes (Nord University, Bodø) and Jan Ludvig Lyche (NMBU).