Stimulatory effects of neuropeptide Y on food intake and growth of Oreochromis niloticus

This study was carried out to investigate the effects of human neuropeptide Y (NPY), administered intraperitoneally (i.p.) or orally on food intake and growth of tilapia Oreochromis niloticus (11.19 g) in two separate experiments. In the first experiment, which lasted for 24 h, NPY was injected intraperitoneally (i.p.) at 0, 0.1, 0.3, 0.6 μg g− 1 body weight (bw). In the second experiment, NPY was given orally at 0, 0.125 and 0.25 μg g− 1 feed for 50 days.In experiment 1, food intake was significantly increased by i.p. administration of NPY at 10 h post-injection, but the stimulation rapidly diminished at 24-h post-injection. Food intake was 39% higher in the group received 0.6 μg g− 1 bw than the control during the first 10 h. In experiment 2, average final weight of the fish fed 0.25 μg g− 1 feed NPY was found to be approximately 12% higher than the control group. Specific growth rate and daily food intake were significantly higher at 0.25 μg g− 1 compared to the control (P < 0.05). Differences in growth rate and feed intake started to appear around the 30th day of culture and this trend remained the same until the end of the feeding. The dose of 0.125 μg g− 1 feed NPY stimulated food intake but not growth. The present results show that NPY either administered by i.p. injection or through feed has stimulatory effects on food intake as well as growth of O. niloticus.