Chemical composition and standardized ileal digestibility of protein and amino acids from blue mussel, starfish, and fish silage in pigs

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Mussels cultured on lines for nine months and harvested in March were boiled to remove shells and processed into a dry meal or a silage acidified by formic acid. Starfish meal was prepared from starfish caught in May, and a starfish juice fraction was obtained by pressing fresh starfish. Commercial fish silage from farmed salmon was also included in the experiment. The standardized ileal digestibility (SID) of crude protein (CP) and amino acids (AA) was evaluated in a Latin square design with pigs (initial weight 39.3 kg) fitted with a simple T-cannula in the terminal ileum. Diets contained 131–162 g CP/kg and 5 g chromic oxide/kg. Endogenous losses of protein and AA were estimated by feeding an N-free diet. On a dry matter (DM) basis, mussel meal contained 605 g, mussel silage 575 g, starfish meal 700 g, starfish juice 393 g, and fish silage 776 g CP/kg. The ratio of AA to CP ranged from 0.83 to 0.87. The content of crude fat was high in the mussel products (157–161 g/kg DM), and the starfish meal and juice were high in ash (203 and 474 g/kg DM) with one-fourth being calcium. The AID of CP was 0.74, 0.81, 0.70, and 0.61 for mussel meal, mussel silage, starfish meal, and fish silage. The SID of CP was 0.83, 0.87, 0.80, and 0.68 for mussel meal, mussel silage, starfish meal, and fish silage. For both CP and AA digestibility, the lowest (P<0.05) was found in fish silage and the highest (P<0.05) in mussel silage. In conclusion, both mussel and starfish products showed chemical characteristics arguing for their use as feedstuffs in pig diets. Processing into silage rather than meal increased the SID of CP and AA, and both mussel products and starfish meal had greater SID compared to commercial fish silage.