ISSUE FOCUS 60 FEED & ADDITIVE MAGAZINE August 2024 herent with formulation to varying total or digestible protein in dose response studies. As a result, estimates of protein requirements may be prone to overestimation where protein content is inflated by specific amino acids being provided in excess in order for minimum requirements of limiting amino acids to be met with available raw materials. In addition, the “protein” content of diets and raw materials, and any requirement estimates based on these analysed contents, are in reality measurements of the nitrogen (N) content (multiplied by varying conversion factors). A certain proportion of this N comes from N-containing compounds not directly used for protein deposition (“non-protein N”, which can constitute up to 20% of total N). This N can be in the form of nucleic acids (not directly used for growth or health maintenance when coming from an exogenous source) or phospholipids and non-proteinaceous amino acids (which are required in varying quantities at different stages of the animal’s lifecycle). By establishing requirements for all individual N-containing compounds, rather than protein as a whole, it is possible to safely reduce oversupply of unnecessary N in feed formulations. Skretting Aquaculture Innovation (Skretting AI) has worked for many years on establishing and re-establishing digestible amino acid requirements for many cultured aquatic species, with changing raw material baskets, and improved understanding of the factors contributing to variations in these requirements. The Skretting AminoBalance concept, launched in 1996, was the first step in optimising dietary N supply through formulation to a defined balance of amino acids modelled across fish size, and based on targeted studies. Through further research and re-establishment and validation of these requirements in numerous controlled studies and field trials, Skretting AI has been able to refine this concept further and launch its latest innovation: AmiNova, a new feed formulation concept that brings an even greater level of precision to fish nutrition. AmiNova is a concept whereby supply of nitrogenous compounds is optimised, reducing the artificial inflation of non-essential N, thereby reducing the excretion and eventual release to the environment of excess N. In developing this concept, Skretting AI Principal Researcher Ramón Fontanillas investigated the interactive effect of varying supply of total digestible N and the supply of amino acids at optimal inclusions, derived from numerous internal Skretting trials over the past 30 years, on Atlantic salmon and rainbow trout (Oncorhynchus mykiss) performance at varying fish size. Adequate supply of the essential amino acids (EAAs, those which cannot be synthesised by the animal) is most often the primary consideration when balancing N in aquatic feed formulations (with some exceptions for non-essential amino acids – NEAAs - with important non-protein functions). NEAAs may, however, become important when EAA supply is limited. When formulating to both protein and amino acid targets, it is assumed that supply of NEAAs, which are also required in a certain ratio for optimal protein deposition, is sufficient. At the same time, many EAAs are artificially boosted above requirement in this situation, allowing excess EAAs to be used for limiting NEAA synthesis, where required. Where this inflation of amino acid levels is not present, such as when formulating with lower or no total N targets, however, utilisation of EAAs could conceivably be influenced by the NEAA content of the diet. As such, the interaction between amino N source and the response to varying total N supply was also investigated in the concept development stage. Results of the concept development trials have shown that reductions in total digestible N were possible in Atlantic salmon diets, without significantly impacting growth or feed utilisation (Figure 1), when all essential nitrogenous micronutrient requirements were met. In addition, dissolved N discharge by Atlantic salmon was observed to be reduced by up to
RkJQdWJsaXNoZXIy MTUxNjkxNQ==