Feed deprivation and re-feeding on alterations of proteases in tilapia Oreochromis mossambicus

Regulation of gastrointestinal proteases becomes particularly important when fish starved. In this work, tilapia (Oreochromis mossambicus) were allotted to various treatments including starvation times (3, 5, and 7 d) and 1 d of re-feeding after various starvation times to test whether food deprivation causes changes in protease activities in the gastrointestinal tract. No significant differences in body weights were found among all groups. The relative stomach weights of the starved groups (3 and 5 d) were significantly higher than those of the control group. The relative intestinal weight of the starved group after 7 d of starvation was significantly higher than that of the control group. Additionally, re-feeding resulted in relative stomach and intestinal weight increases after 5 and 7 d of starvation, respectively. The activity of trypsin (T) in fish subjected to a short starvation period was lower than that in fish fed normally, whereas chymotrypsin (C) activity increased. The T/C ratio decreased with starvation time, indicating the possibility that the growth of tilapia is inhibited by starvation. Furthermore, re-feeding after starvation resulted in increased trypsin and chymotrypsin activities, and a decrease in the T/C ratio compared to before feeding. These data suggest that short-term starvation dampens trypsin activity and the T/C ratio in relation to the growth of tilapia, and that re-feeding consequently stimulates the activities of intestinal proteolytic enzymes in tilapia.