Project Number: 2050-21310-006-013-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Dec 14, 2020
End Date: Jun 30, 2023
We predict that rainbow trout with dissimilar genetic histories possess different innate, mechanistic responses underlying growth and nutrient utilization and that this information can be exploited. To help answer this prediction, we will measure plasma metabolites, and intestinal protein expression along with performance traits among two unique rainbow trout strains after rearing on either a fishmeal or plant protein based diet. The first strain (ARS) was genetically selected by this group for growth and utilization of a high soy protein, plant-based feed and is known to to improved growth, better protein retention, and not develop intestinal enteritis when reared on a high soybean meal diet. The second strain (CL) is a commercial strain, specifically a line only selected for domestication. Contrasts and correlations in metabolome, histology, proteome, and performance will be made between the two strains. The overall goal for this research project then is to determine the molecular mechanisms behind enhanced growth and protein retention and the ability to utilize a high soybean meal diet without developing enteritis in rainbow trout, while also studying the underlying innate physiological changes that occur through dietary selection.
To determine the effects of selection on growth, dietary utilization, and intestinal inflammation two strains of rainbow trout, an ARS selected strain (ARS) and a production line strain (CL), were separated into groups and fed either a fishmeal protein based feed or a fishmeal free plant protein feed containing high levels of soybean protein for seven months. At the levels of soybean meal in the plant based feed it is known that normal strains of rainbow trout developed intestinal inflammation, or enteritis. The selected ARS strain has been shown to not develop enteritis after long term feeding of high soy all plant protein diets. For this experiment both strains were hatched and reared alongside one another. At 5 grams each strain was split into two groups with one group receiving the fishmeal diet (ARS-FM and CL-FM) and the other group reared on the high soybean meal plant-based feed (ARS-PM and CL-PM). Samples were taken at two months after starting on the diets when neither strain should show the development of enteritis and at 7 months feeding when enteritis should be evident in the nonselected strain on the plant based feed (CS-PM). At both time points blood was drawn from 9 fish per treatment and the plasma isolated and kept frozen at -800C. Also at both time points intestinal tissue was taken and flash frozen in liquid nitrogen for proteomic and metabolomic studies and also placed in formalin for histological examination. The fixed intestinal histological samples will be analyzed and should determine the presence or absence of intestinal inflammation and where confirmed the relative level will be recorded through multiple morphological measurements. The plasma samples will by analyzed to qualitatively and quantitatively determine the metabolites present in the plasma from the different treatments. The frozen intestine samples will be analyzed both qualitatively and quantitatively for metabolites and proteins. This information will then be used to determine the physiological differences between the strains related to improved amino acid transportation, growth, and the prevention of intestinal enteritis.