Effects of feeding frequency on gastric evacuation,growth benefit and body composition of juvenile genetic improved farmed tilapia strain of Nile tilapia(Oreochromis niloticus)

A 6-week feeding experiment was conducted to determine the optimum feeding frequency for gastric evacuation,growth performance and body composition of the juvenile genetic improved farmed tilapia strain of Nile Tilapia(Oreochromis niloticus)(GIFT strain of Nile tilapia).At the start of the feeding trial,gastric evacuation rate of the fish was monitored after feeding to visual satiety.Gastric evacuation of the fish was best fitted with square root model.It was estimated that gastric feed contents gradually decreased and reached the pre-feeding level within 15 h and 80% evacuation would require 9 h,which suggested corresponded to the return of appetite.Six replicate groups of the 360 fish(initial weight 3.72 g)were fed to visual satiety puffed feed at different feeding frequencies(four meals a day,three meals a day,two meals a day,four meals every 2 days,three meals every 2 days and two meals every 2 days).As feeding frequency decreased,the weight gain and feed efficiency of the juvenile gradually decreased.The specific growth ratios(SGR)of fish fed four meals a day,three meals a day and two meals a day were significantly higher than those of four meals every 2 days,three meals every 2 days and two meals every 2 days(P<0.05).The feed intakes of fish fed two meals a day,four meals every 2 days,three meals every 2 days and two meals every two days were significantly lower than those of three meals a day and four meals a day(P<0.05).As feeding frequency decreased,moisture contents of fish body increased and the contents of fat and protein decreased gradually,and there were significant difference between the fish fed four meals a day,three meals a day and the fish fed two meals every 2 days.Hepatosomatic indices of fish were not significantly different between all test groups.It is concluded that two meals a day is more effective than other feeding frequencies for improving growth performance or feed efficiency of juvenile GIFT strain of Nile tilapia from 3.7 to 48.0 g.Gastric evacuation is a simple and convenient method to evaluate optimum feeding frequency of juvenile GIFT strain of Nile tilapia.