Seaweed as a protein source for mono-gastric livestock

Background: Seaweeds are often cited as alternative protein sources for livestock due to their global distribution, nutritional profile and independence from terrestrial agricultural resources. Scope and approach: Here, we critically appraise the literature and quantitatively assess seaweeds as a protein source in livestock feeds by assembling a database of amino acid data for 121 seaweed species and comparing the quality and concentration of protein to ‘traditional’ protein sources (soybean meal and fishmeal) and then benchmarking the seaweeds against the amino acid requirements of monogastric livestock (chicken, swine and fish). Key findings and conclusions: The quality of protein (% of essential amino acids in total amino acids) of many seaweeds is similar to, if not better than, traditional protein sources. However, seaweeds without exception have substantially lower concentrations of total essential amino acids, methionine and lysine (on a whole biomass basis, % dw) than traditional protein sources. Correspondingly, seaweeds contain an insufficient concentration of protein, and specifically insufficient essential amino acids, to meet the requirements of most mono-gastric livestock in the whole seaweed form. Consequently, the concentration or extraction of protein from seaweeds will be the most important goal in their development as an alternative source of protein for mono-gastric livestock.