Contribution of Amino Acids in Cereal Grain Products to Precision Feed Formulation for Tambaqui (Colossoma macropomum) Using a Digestibility Approach.

Although cereal grain products have low protein content, they can contribute up to 25% of total protein in low-trophic level/omnivorous fish diets. Thus, understanding the amino acid contribution of these ingredients becomes crucial for meeting the dietary requirements of omnivorous fish. A digestible nutrient basis is essential for precise feed formulation. To address this, we conducted a digestibility trial to assess cereal grain products' gross nutrient and amino acid digestibility for tambaqui, a key species in Latin American aquaculture. Forty-eight tambaquis (400 ± 20 g) were randomly assigned to six 310 L aquaria connected to a recirculating system following a completely randomised block design with five treatments and four replicates. The fish were fed test diets consisting of a 70:30 mixture of the reference diet and test ingredients. Chromic oxide was used in all diets as the indigestible marker at 2 g kg^-1. Results were analysed using ANOVA, and significant differences (p < 0.05) were further assessed using the SNK multiple range test. Our findings revealed that corn and sorghum exhibited higher levels of amino acids and digestible energy than other ingredients. At the same time, broken rice showed the lowest amino acid digestibility and wheat middlings had the lowest digestible energy content. Overall, protein and amino acid digestibility in the feed ingredients ranged from 70% to 99%. These results indicate that tambaqui can efficiently digest plant proteins, even when sourced from carbohydrate-rich ingredients, underscoring the potential of these products in formulating cost-effective diets for this species.