Apparent digestibility of selected feed ingredients for juvenile cobia Rachycentron canadum

Abstract

Apparent digestibility coefficients of dry matter (DM), crude protein (CP), crude lipid (CL), gross energy (GE), phosphorus, and amino acids in Peruvian fish meal, defatted soybean meal/roasted and solvent-extracted, defatted soybean meal/solvent-extracted, poultry meal, meat and bone meal, peanut meal, rapeseed meal, and corn gluten meal were determined for juvenile cobia. A reference diet (RF) and test diets (consisting of 70% RF diet and 30% of the feedstuff) were used with 0.5% Cr 2O 3 as an external indicator. The juvenile cobia, averaging 10 g, was stocked in 300-l fiberglass tanks at a density of 20 fishes per tank. Feces were collected from triplicate groups of fish using a fecal collection column attached to the fish rearing tank. Apparent digestibility coefficients of dry matter, crude protein, crude lipid, and gross energy were highest for fish meal and corn gluten meal. Statistics indicated that apparent dry matter digestibility for juvenile cobia ranged 60.42–87.56% for animal products and corn gluten meal and 58.52–70.51% for soybean meals, peanut meal, and rapeseed meal. The protein and lipid from both plant and animal sources were well digested by cobia. Apparent protein and lipid digestibility ranged 87.21–96.27% and 91.59–96.86%, respectively, for animal products, and 88.97–94.42% and 92.38–96.93%, respectively, for plant products. The cobia demonstrated a high capacity to utilize phosphorus in the ingredients. The apparent phosphorus digestibility ranges of animal feedstuffs and plant feedstuffs were 62.36–71.22% and 56.32–69.76%, respectively. Amino acid availability reflected protein digestibility, except in meat and bone meal, for which the availability of some amino acids was lower, possibly due to protein damage during processing. Digestibility information could promote the use of ingredient substitutions in least-cost formulated diets for cobia.