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

Abstract

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-MTM), white fish meal (WFM), rockfish muscle (RM), 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-MTM were 92.6%, 87.5%, 79.1%, 76.2% and 70.6%. Apparent phosphorus digestibilities of RM, BAIFA-MTM, 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-MTM, CGM and SM (P < 0.05). PER was positively correlated with apparent protein digestibility (r2 = 0.82, P < 0.05).