This project will be divided into two goals. The first goal would be to characterize methionine absorption and gut barrier function along the intestinal tract of Atlantic salmon and rainbow trout in response to a SBM- versus a fishmeal-based diet, supported with gene expression analysis on methionine transporters. Our second goal would be to assess changes to methionine absorption and gut barrier function in response to specific ANF components on a SBM- and fishmeal-based diet.

1. Conduct a 12-week feeding trial on Atlantic salmon and rainbow trout using a SBM-based (0% FM; 25% SBM; 23% SPC) and fishmeal-based diets (28% FM; 0% SBM; 0% SPC).
2. Characterize gut transport kinetics of methionine and assess gut barrier function along the intestine of Atlantic salmon and rainbow trout in response to SBM- and fishmeal-based diets, respectively, using Ussing chambers, supported with gene expression analysis on methionine transporters.
3. Assess changes to methionine transport and gut barrier function along intestinal segments taken from fish fed either a SBM- or fishmeal-based diet in response to specific ANF components.

1. Further our understanding on how SBMIE-affected intestinal segments influence absorption of methionine in comparison to a fishmeal-based control diet
2. Provide the first characterization and identification of specific ANF components that hinder methionine absorption and gut barrier function in salmonids
3. Further our understanding of the impacts of SBM on gut function in order to design fish feed with higher inclusion levels of SBM for salmonids without compromising fish health and growth

Updated July 12, 2024:
We have completed the purchase of the Ussing chamber (7/8/2024) and are in the process of its setup and calibration. This includes setting up the software and accessory equipment, as well as conducting preliminary experiments on trout intestinal tissues. These preliminary experiments will be cross-referenced with previously published research with Ussing chambers in trout to ensure accuracy of results and proper functioning of this machine. All chemicals (i.e.: physiological buffer components, isotope, etc.) and accessory equipment (i.e.: gas tanks, water bath chillers, etc.) required for the Ussing chambers have been purchased to establish baseline characterization of methionine transport in both salmon and trout. During the measurements of methionine transport, flux samples taken from the Ussing chamber will be measured on a liquid chromatography-mass spectrometry instrument (LC-MS). The facility required to perform the LC-MS measurements has been set up, with a technician present to help with its troubleshooting and analysis. Finally, we have been growing trout and salmon to an acceptable size (~300-400g) for the Ussing chambers to complete baseline characterization experiments. Intestinal tissue samples will be collected and frozen (-80oC) for gene expression analysis for Year 2 – Q4.

View uploaded report

Updated September 17, 2024:
The setup of the Ussing chamber has been completed, including the purchase and calibration of accessory equipment (i.e.: gas tanks, refrigerated recirculating water system, DMMC6 membranes included with the Ussing chambers, etc.). We designed preliminary experiments to test the proper functioning of the Ussing chamber and its software. This included running trout intestinal tissues on the Ussing chambers to measure transepithelial electrical resistance (TEER). Briefly, TEER measurements along the intestine can indicate differences in barrier function/integrity/resistance of those segments. The data generated from these preliminary experiments will also establish an expected baseline for TEER measurements from rainbow trout. Similarly, TEER experiments will be conducted in Atlantic salmon along the intestinal segments.

These preliminary results demonstrated significant differences in TEER between all segments except for the posterior proximal and distal segments, suggesting differences in barrier function along the intestinal tract. Interestingly, the anterior proximal has the highest TEER compared to the other segments, suggesting a more resistant tissue with higher barrier function (less paracellular activity). In contrast, the following mid segment has the lowest TEER, suggesting lower barrier function and possibly higher paracellular activity.

Finally, the measurement of methionine transport from the Ussing chamber will be performed on a liquid chromatography-mass spectrometry instrument (LC-MS). The facility that will perform the LC-MS analysis for our methionine transport will be expected to start our sampling and analysis in the beginning of October. Therefore, our methionine transport experiments, as well as the effects of anti-nutritional factors on methionine transport, will be commencing in mid-September, followed by the shipment and analysis of our samples in October.

If our research is successful, we can project to design SBM-based diets for salmonids with higher inclusion levels of SBM, without causing harm to fish health and growth. This will provide soybean farmers with many benefits, including the increased inclusion of soy in aquaculture diets resulting in increased sales and profits for farmers, as well as promoting the beneficial impact of SBM incorporation into fish feed, which will increase the overall demand for soy. Additionally, if we use this technique to study nutrient absorptive mechanisms in response to SBMIE and ANF components in other aquaculture species, we can also increase SBM levels in those diets, again increasing the demand for soy and benefits to soybean farmers. Overall, if our projections are correct, soy has the potential to improve its standing as the leading plant-based alternative for fishmeal in aquaculture diets.