Nile tilapia (Oreochromis niloticus): enteroendocrine peptides and functional amino acids

Abstract

The present thesis provides research findings in two different approaches. The first study analyzed by immunohistochemistry the distribution of ECs producing gastrin (GAS), cholecystokinin-8 (CCK-8), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP) along the gut of Nile tilapia. In addition, we assessed the effects of fasting and feeding in the distribution of immunoreactive ECs. Depending on the peptide produced and anatomical location, ECs were seen more concentrated in some segments while in other intestinal portions ECs were sparse. Regarding nutrient status, we found that the anterior segments of the midgut seem to be the main site which respond to luminal changes in Nile tilapia. The second study investigated the effects of dietary supplementation of glutamine and arginine for Nile tilapia. The fish were fed the six experimental diets formulated to contain different levels of supplemental Gln and/or Arg (Control, GLN 1%, GLN 2%, ARG 1%, ARG 2% and GLN+ARG 1%) for a nine weeks period. Growth performance, innate immune responses, and amino acids profile in plasma and whole-body were examined. Dietary Gln and/or Arg supplementation resulted in significant effects on weight gain, feed intake, feed efficiency ratio, protein efficiency ratio and protein retention. Moreover, the concentration of free AA in plasma at 6 h and 18 h were significantly affected by experimental diets.