In vitro digestion method to evaluate solubility of dietary zinc, selenium and manganese in salmonid diets

In-vitro digestion models: a critical review for human and fish and a protocol for in-vitro digestion in fish

Digestive systems in human, animals, and fish are biological reactors and membranes to digest food and extract nutrients. Therefore, static and dynamic models of in-vitro digestion systems are developed to study e.g. novel food and feed before in-vivo studies. Such models are well developed for human, but not to the same extent for animals and fish. On the other hand, recent advances in aquaculture nutrition have created several potential fish meal replacements, and the assessment of their nutrient digestibility is critical in the application as a fish meal replacement. Using an in-vitro method, the assessment of an ingredient digestibility could be faster and less expensive compared to using an in-vivo experiment. An in-vitro method has been widely used to assess food nutrient digestibility for humans; however, its application for fish is still in the early stages. Both the human and fish as monogastric vertebrates share similar gastrointestinal systems; thus, the concept from the application for humans could be applied for fish. This review aims to improve the in-vitro digestion protocol for fish by adapting the concept from then study for humans, summarizing the current available in-vitro digestion model developed for human and fish in-vitro digestion study, identifying challenges specifically for fish required to be tackled and suggesting an engineering approach to adapt the human in-vitro gastrointestinal model to fish. Protocols to conduct in-vitro digestion study for fish are then proposed.

Effect on amino acid and mineral content of the loach (Misgurnus anguillicaudatus) by adding Fe (II) chelating hairtail protein hydrolysates (Fe (II)-HPH) to the feed

To study the effect on amino acid and mineral content of the loach meat by adding Fe (II) chelating hairtail protein hydrolysates (Fe (II)-HPH) to the feed. A total of 100 healthy loaches were selected. After 1 week's adaptive feeding, they were randomly divided into five groups and fed with feeds containing of Fe (II)-HPH (0, 0.5, 1, 2, and 4 g/kg). On the 40th day, detection work of general nutrients (moisture, ash, crude protein, and crude fat), mineral elements (Fe, Mn, Cu, Zn, Na, K, and Ca), amino acid and amino acid score (AAS), Chemical Score (CS) and essential amino acid index (EAAI) indexes were done. The results show that crude protein has the highest content while crude fat has the lowest when amount of added Fe (II)-HPH in feed is 2 g/kg. The Fe content is significantly improved while amount of added is 1, 2, 4 g/kg. The Ca content is significantly improved and the Zn content is significantly improved while amount of added was 2 g/kg. Mn contents are significantly lower than control while amount of added is 4 g/kg. Based on analysis of amino acids in each group, the nutritional value of loach meat with 2 g/kg Fe (II)-HPH addition amount is relatively high, total amount of essential amino acids increases significantly, and EAA/TAA and EAA/NEAA improve significantly. In conclusion, adding 2 g/kg Fe (II)-HPH to feed could improve the nutritional values of loach meat.