Dietary total phosphorus supplementation in goldfish diets
ABSTRACT. Although goldfish (Carassius auratus) is an important species for the ornamental fish industry, few data are available regarding the nutrient requirement of this species, with emphasis to mineral nutrition. Thus, we designed a 45-day feeding trial to evaluate the effect of dietary total phosphorus (P) levels on growth performance and carcass mineral composition of goldfish fingerlings. 210 goldfish with 1.18 ± 0.04 g were randomly stocked into 30 3L-aquaria in a completely randomized design. Test diets were formulated to contain the following dietary total P levels: 3.5, 6.5, 9.5, 12.5 and 15.5 g kg-1. Dietary P affected all growth parameters and carcass macrominerals deposition, however, the micromineral carcass composition was not affected. No P deficiency signs were observed throughout the experiment. The linear broken-line model best fitted to daily weight gain, feed conversion ratio, specific growth rate, protein efficiency ratio, P retention, and whole-body P concentration at 8.2, 11.4, 8.2, 11.4, 15.5 and 7.1 g kg-1 dietary P, respectively. An exponential model best fitted to phosphorus utilization data with an estimated requirement of 8.6 g kg-1. In sum, the use of total P levels between 7.13 and 11.4 g kg-1 in goldfish diets seems to meet the requirement for maximum growth, feed utilization and proper whole-body mineralization.