Total ammonia nitrogen excretion rates and feces production rates as an index for comparing efficiency of dietary protein utilization of offsprings from selected Korean strain, cultured Japanese strain and their intraspecific hybrid strain of juvenile Red Sea bream, Pagrus major

Abstract

An experiment was conducted to investigate the differences of total ammonia nitrogen (TAN) excretion rates and feces production rates among the offsprings from cultured Japanese strain (JJ, mean BW; 17.1 ± 0.1 g), intraspecific hybrid strain between cultured Japanese and selected Korean strain (JK, mean BW; 17.1 ± 0.1 g) and selected Korean strain (KK, mean BW; 21.5 ± 0.1 g) of red sea bream in order to compare their dietary protein utilization efficiency. Fish were hand-fed with a commercial diet containing 46.7% crude protein for 2 weeks, three times daily 09:00, 13:00 and 17:00. After daily feeding, the TAN excretion rates reached peaks of 49.03, 58.75 and 36.26 mg/kg fish/hr for the JJ, JK and KK strain, respectively, during the daytime. The value of the KK strain was significantly lower than that of the JJ and JK strain (P<0.05), however daily TAN excretion rates of the JJ, JK and KK strain were not different (P>0.05). When fish were fed at satiation after 4 days of starvation, TAN excretion rates reached the maximum values 4 hours after the feeding for the KK (31.23 mg/kg fish/hr and 6 hours after the feeding for the JJ (44.19 mg/kg fish/hr) and JK strain (41.70 mg/kg fish/hr). After 3 days of starvation, the daily endogenous TAN excretion rates (ETE) for the JJ, JK and KK strain were 286.91, 215.66 and 179.29 mg/kg fish/day, respectively. The value of the KK strain was lower than that of the JJ and JK strain (P<0.05). The total feces production rates of the JJ, JK and KK strain were not significantly different, however the proportions of feces production rates by time for the JJ, JK and KK strain were different (P<0.05). As overall results, efficiency of dietary protein utilization of JJ, JK and KK seems to be different and KK strain could offer a desirable option for aquaculture purpose.