Silage from tropical fish 2. Undigested fraction

Summary The solubility of the undigested fraction (sediment) of a silage made from silverbelly (Leiognathus sp.) in sodium dodecyl sulphate, guanidine hydrochloride and 2-mercaptoethanol, alone and in combination was evaluated. The sediment was probably composed of muscle proteins cross linked by disulphide bonds and stabilized by hydrophobic associations and hydrogen bonds. Ensilation followed by in vitro digestion of the sediment with pepsin/pancreatin/trypsin or in vivo digestion of the sediment using chicks, solubilized about 81% and 90% respectively of total nitrogen in silages up to 14 days old. The most resistant fraction was rich in collagenous derived material and bones. It is suggested that controlled ensilation can produce a highly digestible protein source without the formation of large amounts of reactive and labile free amino acids.