Assessment of soybean meal in diets for discus (Symphysodon aequifasciata HECKEL) farming through a fishmeal replacement study

Abstract

A 12-week feeding trial was carried out with discus (Symphysodon aequifasciata HECKEL), a valuable ornamental species produced in South East Asia, to determine the suitability of using soybean meal as a partial fishmeal substitution in the diet. Juvenile discus (4.3–4.8 g) was fed eight experimental diets with graded levels of soybean meal replacing fish meal (0%, 10%, 20%, 25%, 30%, 35%, 40%, 50%). Growth performance (relative growth rate, specific growth rate) decreased and feed utilization (feed conversion ratio, protein efficiency ratio) was worsened at 30% replacement and higher. Amino-acid analysis indicated methionine and lysine deficiencies at dietary high soybean replacement levels, although the essential amino-acid requirements for this species are unknown. The level of soybean in diets negatively affected both dry matter and protein digestibility. This present trial showed the need for further studies involving amino-acid supplementation, different soy products and palatability enhancement to improve utilization of diets containing soybean meal to allow higher than the maximum 30% replacement level suggested here.