Voluntary feed intake and transition of ingesta in the gastrointestinal tract of juvenile cobia (<i>Rachycentron canadum</i>) feed different diets

Abstract

    This study aimed to evaluate the palatability of a plant based protein diet (BL/A), with high inclusion levels of plant protein sources but balanced in lysine to arginine ratio (1.1), compared to two locally commercial pellets CD1 (Uni-President, Ltd.) and CD2 (INVE, Ltd.), and the transition of ingesta in juvenile cobia. Juvenile cobia were fed to satiety with each of the three diets had equal feeding rate of 5.3-5.4±0.3% BW (for a meal). No differences in stomach filling occurred between cobia fed the PBD diet and those fish fed the CD1 or CD2 diet. Gastric evacuation rates in cobia were performed as an exponential relationship, and were estimated as the function V_T=V₀ e^-b(x) (V_T, volume of feed at time T; V₀, volume of feed at time 0; b, the instantaneous evacuation rate; and x, time postfeeding; R²>0.95). Between 77 to 80% of the stomach contents were evacuated to the lower parts of the gastrointestinal tract at 8 h, and most of consumed feed (98%) was emptied out of the stomach at 16 h postfeeding. This was supported by the fact that cobia had good appetite in the 2nd feeding of the day. Time required for the return of appetite in cobia was within 8 h after feeding to satiation.

Key words: Cobia, lysine, arginine, evacuation