Amino Acid Analysis in Feed and Feces

Amino acids in feed ingredients, diets, and fecal material were determined according to the protocol described by AOAC [42 ]. As such, dry ground samples were digested with 4 mol L⁻¹ methane sulphonic acid (Sigma-Aldrich, St. Louis, MO, USA), and AAs were determined by using a programmed automatic amino acid analyzer (L-8900; Hitachi, Japan). Detection used a post-column derivatization method with ninhydrin (520 nm, for the total acid content). A suite of amino acid concentrations as external standards, including L Norleucine (synthetic amino acid) addition as the internal standard within the sampling protocol and digestion stage, dilution, and injection (20 µL) was employed. However, the apparent nutrient digestibility coefficients (ADCs, %) and Amino Acid profile (% of digestible amino acid basis) of the FM and CM were presented in Table 3.
Apparent net protein utilization (ANPU, %) and phosphorous retention (PR, %) in feeds and fish were determined according to the method of Palma et al. [49 (link)]: