Digestibility, protein retention rate and ammonia excretion in juvenile fat snook (Centropomus parallelus) fed with different protein levels

Digestibilidade, taxa de retenção proteica e excreção de amônia em juvenis de robalo-peva (Centropomus parallelus) alimentados com rações com diferentes níveis de proteína

ABSTRACT:

The aim of this study was to determine the level of dietary crude protein (CP) (480, 400, 440, 520 and 560g kg^-1) in rations for juvenile II fat snook (Centropomus parallelus) that best promotes protein absorption and lower excretion of nitrogenous products. Three experiments were conducted: the first assessed the protein retention rate; the second evaluated ammonia excretion; and the third determined the best digestibility coefficient. The estimated protein retention rate showed a positive quadratic response to dietary CP with maximum retention at the 510.20g kg^-1 protein level, and increasing levels of protein resulted in a greater total ammonia excretion rate in water. The mean apparent protein digestibility coefficient values increased with increasing levels of dietary protein up to 520g kg^-1, where they stabilized. As determined by regression, the level of dietary CP that promotes the best digestibility was 495.62g kg^-1.

Key words:
crude digestible protein; fish culture; nitrogen excretion; diet