The effect of different starch levels on oxygen consumption and nitrogen excretion of Eurasian perch (Perca fluviatilis)

Abstract: Aquaculture is one of the fastest-growing and valuable industries nowadays. Because fish meal and fish oil are the major components of fish diets, there is growing concern that the rapid growth of this industry will lead to either fish meal scarcity or the depletion of marine fish population. Fish utilize parts of protein and oil in their diets only as sources of energy. Therefore, parts of the aforementioned substrates are replaceable by other sources of energy such as digestible carbohydrates. Nonetheless, fish have limited ability to assimilate carbohydras and consequently, species-based research is needed for determining the appropriate level of carbohydrates in fish diets. An indirect calorimetry study was performed on Eurasian perch using diets with four different levels of raw wheat starch (0%, 10%, 20% and 30%). We measured oxygen (OC) consumption and ammonia excretion (AE) in response to different carbohydrate levels. The OC was not significantly different between treatments but the results showed numerically decreasing values (1.62- 1.15 mg min-1 kg-1BW) with increased inclusion of starch in the diet. The fish consumed more oxygen on the second experimental days compared with the first experimental days (P=0.001).The ammonia excretion was highest in 0% and 30% Starch diets and lowest in fish fed 10% Starch, which indicated that 10% inclusion caused a protein sparing effect. Based on the results of our experiment, the inclusion of 10% raw starch in the diet of Eurasian perch appears to be beneficial and unproblematic.