While rainbow trout are carnivorous, a selected strain performs well on a soy-based feed ― and tolerance of this vegetarian diet is linked to 63 genes, according to a study published in the open-access journal PLOS ONE by Jason Abernathy and Ken Overturf from USDA-ARS, USA, and colleagues.
The main source of protein in aquaculture feeds is fishmeal, which is costly and insufficient to support long-term growth of the industry. However, replacing fishmeal with plant proteins has been problematic: a plant-based diet reduces salmonid growth, and soy and other legumes can cause severe enteritis in these fish. Previously, Abernathy, Overturf and colleagues selected a strain of rainbow trout that tolerates a high-soy, all plant-protein feed: the fish grow well and do not have enteritis.
In the new study, the researchers identified candidate genes that are critical to the rainbow trout strain’s tolerance of a soy-based diet. The researchers compared non-selected and selected rainbow trout raised for 12 weeks on either a fishmeal-based feed or a high-soy, all plant-protein feed. Functional genetic analyses included differential gene expression, co-expression, and metabolic pathway mapping in two tissues (muscle and liver).
The researchers identified 63 candidate genes for tolerating the high-soy diet in rainbow trout. These genes may be useful markers for developing the trait of plant-diet tolerance in fish. The researchers also found that the most perturbed pathway was that for purine metabolism, which encompassed 152 sequences representing 25 enzymes. Meat and seafood products are generally higher in purine than plant products, and soybeans are among the more purine-rich plant materials.
In addition, the researchers identified risk loci which are also implicated in human inflammatory bowel diseases, suggesting that rainbow trout selected for plant-diet tolerance may have potential as a biomedical model for ulcerative colitis and celiac disease.
Image Credit: Angelena Sikora/USFWS, Flickr
Reference: Abernathy J, Brezas A, Snekvik KR, Hardy RW, Overturf K (2017) Integrative functional analyses using rainbow trout selected for tolerance to plant diets reveal nutrigenomic signatures for soy utilization without the concurrence of enteritis. PLoS ONE 12(7): e0180972. https://doi.org/10.1371/journal.pone.0180972