Apparent protein and phosphorus digestibilities of five different dietary protein sources in Korean rockfish, Sebastes schlegeli (Hilgendorf)

A 6-week feeding trial was conducted to determine the apparent protein and phosphorus digestibilities; in order to evaluate five different dietary protein sources in juvenile Korean rockfish, Sebastes schlegeli. Five diets containing fish meal analog (BAIFA-M(TM)), white fish meal (WFM), rockfish muscle (EM), soybean meal (SM) or corn gluten meal (CGM) were prepared by mixing a basal diet (BD) with one of five test ingredients at the ratio of 7:3. As a reference diet, BD contained three different protein sources, such as casein, gelatin and rockfish muscle. Fish averaging 3.1 +/- 0.03 g (mean +/- SD) were distributed to each aquarium as a group of 20 fish reared in the recirculating system. Fish of triplicate groups were fed one of six experimental diets (BD + five test diets). Apparent digestibilities of dry matter, protein and phosphorus of six diets were determined by the chromic oxide (Cr2O3) method. After 6 weeks of the feeding trial, apparent protein digestibilities of RM, WFM, CGM, SM and BAIFA-M(TM) were 92.6%, 87.5%, 79.1%, 76.2% and 70.6%. Apparent phosphorus digestibilities of RAJ, BAIFA-M(TM), WFM, CGM and SM were 77.5%, 66.9%, 59.5%, 22.2% and 12.6%. The protein efficiency ratio (PER) ranked with RM > WFM, BD > BAIFA-M(TM), CGM and SM (P < 0.05). PER was positively correlated with apparent protein digestibility (r(2) = 0.82, P < 0.05).