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Research Project: Enhanced Alfalfa Germplasm and Genomic Resources for Yield, Quality, and Environmental Protection

Location: Plant Science Research

Title: Evaluation of alfalfa (Medicago sativa L.) foliar protein extracts for use in aquaculture feeds

Author
item COBURN, JESSICA - University Of Minnesota
item WELLS, M SCOTT - University Of Minnesota
item SHEAFFER, CRAIG - University Of Minnesota
item RUAN, ROGER - University Of Minnesota
item Samac, Deborah - Debby

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2021
Publication Date: 6/15/2021
Citation: Coburn, J., Wells, M., Sheaffer, C.C., Ruan, R., Samac, D.A. 2021. Evaluation of alfalfa (Medicago sativa L.) foliar protein extracts for use in aquaculture feeds. Agrosystems, Geosciences & Environment. 4(2): Article e20184. https://doi.org/10.1002/agg2.20184.
DOI: https://doi.org/10.1002/agg2.20184

Interpretive Summary: Protein in feeds for aquaculture, a rapidly expanding food sector, has traditionally been supplied by fishmeal. However, supplies of fishmeal are limited and new sustainable protein sources are needed. Alfalfa produces high concentrations of protein in its foliage. Five methods of producing alfalfa protein concentrate (APC) from foliage were tested for use as a component in aquaculture feeds. Acid-based precipitation methods resulted in the largest recovery of APC (134-142 g/kg dry matter), while heating produced the highest concentration of protein (51% of dry matter) and highest combined concentration of the three most important amino acids for aquaculture feeds, methionine, lysine, and threonine (5.5% of dry matter). The percentage of fatty acids and sugars varied significantly by precipitation method. All methods resulted in low (0.6-1.2%) fiber concentrations. Yields of APC were not significantly different whether produced from total foliage or from leaves removed from foliage using a mechanical stripper. However, the press residue from leaves had high relative feed values, suitable for feeding to lactating dairy cows. These results show that APC is highly suitable as a source for protein and fatty acids for use in aquaculture feeds. Refining alfalfa into multiple products, APC and a protein rich press residue, could increase value of the crop and enhance its utilization on the landscape to protect soil and water resources.

Technical Abstract: Alfalfa (Medicago sativa) is grown worldwide as a high protein forage crop used primarily for feeding dairy and beef cattle. However, its utility as a protein source for other farmed animals and for human nutrition has been largely overlooked. Here, we measured protein concentration, amino acid composition, and percentage of fatty acids, sugars, and fiber in alfalfa protein concentrate (APC) derived from processing alfalfa foliage from a biomass-type variety to evaluate its use as a component in aquaculture feeds. Five methods of producing APC from a press filtrate of alfalfa foliage were tested. Acid-based precipitation methods resulted in the largest recovery of APC (134-142 g/kg dry matter), while heating produced the highest concentration of protein (51% of dry matter) and highest combined concentration of the three most important amino acids for aquaculture feeds, methionine, lysine, and threonine (5.5% of dry matter). The percentage of fatty acids and sugars varied significantly by precipitation method. All methods resulted in low (0.6-1.2%) fiber concentrations. Yields of APC were not significantly different whether produced from total foliage or from leaves removed from foliage using a mechanical stripper on a dry matter basis of starting material. However, the press residue from leaves had higher relative feed values, suitable for feeding to lactating dairy cows, than the press residue from total foliage. Extraction of APC from a reduced-lignin variety or variety with improved forage digestibility did not result in higher protein extraction than that recovered from a conventional variety. These results show that APC is highly suitable as a source for protein and fatty acids for use in aquaculture feeds. Refining alfalfa into multiple products, APC and a protein rich press residue, could increase value of the crop and enhance its utilization on the landscape.