Whole-body amino acid composition of adult fancy ranchu goldfish (Carassius auratus).

Aqua feeds should be formulated to provide complete and balanced nutrition to achieve optimal health and growth in fish, including adequate levels of essential amino acids (EAA). There are few or no data relating to the EAA requirements for ornamental fish species, with the majority of quantitative data for these nutrients being available for commercially farmed fish. The determination of EAA requirements is usually established through dose-response studies, which can be costly and time consuming, especially if determining the requirement for many amino acids (AA). An alternative method for predicting the EAA of fish, which is also relatively fast and inexpensive, is the assessment of whole-body AA composition. A total of eight goldfish with a mean wet weight of 34.2 (SEM 1.4) g were obtained as a result of a routine cull by breeders. The fish were freeze-dried and AA was content analysed by hydrolysis or performic 'acid' oxidation. EAA values ranged between 0.97 (SEM 0.02) for tryptophan and 7.9 (SEM 0.14) for lysine (g/100 g AA). Compositional data were also used to estimate the essential amino acid ratios of these fish. The findings are in agreement with those for juvenile common goldfish, suggesting that there are no differences in whole-body AA composition between juvenile and adult, or fancy and common goldfish. However, these indices do not provide a quantitative total amount of each AA required by the fish, but can be used proportionally to provide guidelines to formulate diets for ornamental species.