Experimentalfishandfishculture
The Nile tilapia used in this study were reared at the Suranaree University of Technology Farm (SUT Farm; Nakhon Ratchasima, Thailand). The experimental Nile tilapia were all male fish that were produced by feeding the swim-up fry with a 50 mg kg−1 17-methyltestosterone-supplemented diet for 4 weeks and then with a diet consisting of 350 g kg−1 crude protein until the experiment started.
Twenty cement ponds (2×2×1m3) (i.e., four replicates of five treatments) were used for the experiment. They were randomly assigned to each treatment diet, and 30 fish (42–47 g) were randomly distributed into each cement pond containing water (depth, 0.7 m) under continuous aeration and with continuous water flow (5 L min−1 ). In addition, a flow-through water change system was implemented by replacing one-third of the water in each pond with dechlorinated water every week. To acclimatize the Nile tilapia to the experimental conditions, the fish were fed the basal diet for 2 weeks. Throughout the experimental period, the fish were hand-fed ad libitum twice daily, and daily feed consumption by replicate was recorded to determine feed utilization