Rearing of coregonid ( Coregonus schinzi palea Cuv. et Val.) larvae using dry and live food : II. Oxygen consumption and nitrogen excretion

Abstract

Postprandial metabolic changes in 5-week-old coregonid fry were measured after feeding with live food, Artemia nauplii and three compound dry diets. Growth rates of fish were different and so were the mean weights of the different groups of fish used in these studies; 167 mg for fry fed Artemia and 53, 104 and 142 mg for fish fed diets 1, 2 and 3 respectively. During the week preceding the measurements, the growth rate was 8.12, 4.54, 6.51 and 9.03% day −1 respectively. There was an increase in ammonia and urea excretion in fed fish in comparison with fasted controls and, in the case of urea, this difference was maintained over 14 h after a meal at 13.5°C. An increase in nitrogen (ammonia + urea) excreted after 2 h of feeding in comparison with unfed fish accounted for 9.16–36.92% of nitrogen consumed. During the 5th week of the experiment, nitrogen retention (the proportion of nitrogen gain to nitrogen consumed) amounted to 38.2% in fish fed Artemia and between 11.5 and 20.9% in fish fed dry diets. Postprandial increase in oxygen consumption (specific dynamic action, SDA) was separated from an increase due to activity. SDA accounted for 28.7% of the energy consumed in fish fed live Artemia, whereas in fish fed artificial diets, the SDA was inversely related to their growth rate, and accounted for 4.9–12.7% of energy intake.